Snorkelling without fear

an essential freediving course to become confident in the sea

by Dr J Floor Anthoni (1998)

Most people who have learnt to swim, also enjoy swimming in the sea. Equipped with mask and fins, they can observe the underwater world, while covering large distances, powered by their fins. But most snorkellers stay on the surface, unable to go down. This chapter teaches you the techniques to go down and 'stay down' for long enough to completely change your snorkelling experience. Anyone can do it, and once you've mastered it, you've mastered a skill for life, for you can do it anywhere in the world where the water is clear enough. A mask and fins then permanently belong to your travel suitcase. Read on, then try it out and don't ever give up!



snorkelling with schools of fish, blue maomaoI have always loved to swim in the open waters of rivers, lakes and the sea. But since I've learned how to snorkel dive with mask and flippers, my fascination for the underwater world has become unstoppable. With my mask I can clearly see what lives down there and my flippers give me the power to swim far and safely and to go deep and return safely to the surface. It has taken me a long time to master the techniques of skin-diving and to train myself to go deep and to stay down for a long time. But then I wondered why it had taken me that long to learn and whether I was really any different from anyone else. To cut a long story short, I discovered that the capacity to stay under is present in everybody and that the main technique of snorkel diving is to preserve energy, and to overcome your fears. Anybody could learn how to become a good snorkel diver in a very short time. It is true that one becomes better at it through practice but it takes a very long time of practice to become any better at it than the average person. In this essential snorkel course I will try to set out my newly discovered techniques and suggest a training schedule to prepare you for it. As you may notice, I'll pay a lot of attention to you before you'll even get wet. You can do all this yourself and it is entirely free!

snorkelling is for the whole family
f020020: snorkelling can be an enjoyment for the whole family because even young children can keep up with their parents. And there is so much to share and learn.
snorkelling in a marine reserve with big fish
f010221: the advantage of snorkelling in marine reserves, is that the fish there have become used to people. There is usually also more fish and they are bigger too.

-- Seafriends home -- school index -- sitemap -- Rev 20060926,20070808,


What do you need?

Here are the things I want you to do to discover whether you can do the course:
    1. You must be comfortable in the water. You can only be comfortable if you can swim a little, although being able to swim well is not really needed in order to snorkel dive.

    2. You must be able to 'pop' your ears by squeezing your nose and 'sneezing'. This blows air through your internal nose passages and you will hear your ears 'click'. This is necessary so you'll be able to go deeper than 2m. Try it now. If it doesn't work, try again, and again.

So lots of people can start and finish the course.


Overcome your fears

The most important start is to overcome your natural and unnatural fears. The slightest amount of fear will make your heart run faster and will reduce your ability to hold your breath. The instructor will help you to overcome your fears.
You must have dealt with all your fears before you go further. Talk to your instructor about them!
diver follows long-tailed stingray Dasyatis thetidis
f029214: a snorkeldiver follows a long-tailed stingray (Dasyatis thetidis) as it takes off from the sandy bottom.
snorkeldiver and long-tailed stingray
f029221: snorkeldiver and long-tailed stingray. These stingrays are quite relaxed about people.


Holding your breath

Being able to hold your breath is very important. Before you go into the water, you must understand how your body reacts to a lack of air. We do that in a number of steps. Take a stopwatch or clock with a seconds-hand.
At this point I want you to understand what is going on in your body. First it uses up the oxygen in the lungs but after 6 seconds there's none left. So it makes very little difference whether you hold air in your lungs or whether you breathe all out. Then the body uses up the oxygen in the blood. That takes about one minute. Then it starts to steal oxygen from all the big muscles in your body. Eventually you will feel very 'tired' very suddenly. This is the danger point. You should avoid getting to this point. But you can try it outside the water.

What makes that some can hold their breath longer than others?

    1. WILLPOWER. Holding your breath and feeling asphyxiated is unpleasant but you'll get used to it. It will be easier when you can look at fishes, play with and octopus and swim through the seaweeds. If you really WANT to become a good snorkel diver, you'll have to learn how to PUSH yourself. This self-control may come in handy for other pursuits.
snorkeller inside a small cave
f044504: in tropical waters a wetsuit is often not needed, and this removes all impediments. Here a snorkeller inspects a small cave in a deep coral reef pool.
f044522: in a deep coral reef pool, a snorkeldiver discovers colourful fishes. Snorkelling in clear warm waters, full of sea life is an unforgettable experience.


The mask

The scuba mask is the most important piece of snorkel equipment. The flat glass and the air between it and your eyes, allow you to see the underwater world clearly. It is the first to put on and the last to take off. Make it a habit to keep your mask on, particularly in harrowing circumstances.

Don't buy a transparent (silicone) rubber mask because these reflect the sunlight into your eyes while looking down. These masks are sort of okay for divers but a no-no for snorkeldivers. Silicone masks are weak and can be damaged easily but they last longer when treated gently. Rubber masks can eventually 'rot' away. Ironically, rubber masks last longer when not rinsed in fresh water after the dive. The salt on it will dry and kill micro-organisms that dine on its natural rubber.

Your mask must have glass windows, not plastic. Plastic is very cheap but it scratches easily and fogs up constantly. The window should be of one piece or of two pieces but rigidly joined together. Swimming goggles would not allow you to see clearly under water. They show a double image. The glass itself is 'tempered' to make it hard and strong and to make sure that it pulverizes into small squares, should it break. Check for the 'T' mark or the word 'Safety'. The mask must fit over your nose so you can let air in. In order to be able to squeeze your nose (to compensate the pressure in your ears) it is best to buy a mask with a nose. Avoid fluoro colours. It scares fish unnecessarily. Choose a blue or black mask.

A new mask has all sorts of grease on its windows. Use toothpaste and plenty of patience to rub it clean. Silicone masks stay greasy almost all of their lives. They need more frequent cleaning with tooth paste.

To test whether a mask fits your face, pull the mask strap back and snuggle the mask onto your face. Then suck it in place. It should stay on your face and not fall off. It shouldn't leak air.

The best way to put a mask on is to put it on your forehead first while pulling the strap over your head. Then lift the mask and snuggle it onto your face while removing your hair and hood from the mask's seal. But adjust your straps first. Many people have their straps too tight, which is uncomfortable, and deforms the mask. It then starts leaking.

Before you put a mask on, spit into it. One good spit for each window. Then rub it in. Wash it off with only one rinse. Splash some water onto your face to cool it off. This closes the pores in your skin and reduces fogging. I always do the outside too. It allows me to see better above the water.

Did you know that it is not the glass in the mask that makes you see under water? It is the air inside the mask that does it. Our eyes are water lenses and they work only because we have air on the outside. With our eyes in the water, the water lens no longer works, and we see blurry. So a mask must be air-tight.


The snorkel

It's almost impossible to buy the right snorkel, these days. Most are too short and too wide. They also have all sorts of gadgets like valves and fancy bends and corners.

Most important is the correct diameter. Your snorkel should not be wider or narrower than your index finger for performance freediving and your little finger for recreational snorkelling. Stick it into the pipe to select the right size. A wide snorkel is difficult to blow clean. A narrow snorkel may hinder the passage of air. If in doubt, take the narrower one because when snorkel diving, one usually doesn't breathe fast. It is more important to be able to blow the snorkel clean. However, for fast swimming on the surface, the snorkel must be wider to let air pass through with ease.

Your snorkel should be long, in order to poke out above the waves. It should stick out at least 8 cm over your head. Your snorkel should have a simple shape, a short bend under the mouth and a long bend to curve around your face. The mouth piece should be strong and durable and it should fit into YOUR mouth. Your lips go over the flap while your teeth bite into the knobs. These should be big enough to open your mouth sufficiently for the air to pass between your teeth. Many snorkels these days, do not satisfy these requirements. Take your time to buy the right one, and don't forget that price has nothing to do with it. My own snorkel cost US$4.

The flippers

The best flippers (or fins) are also the cheapest. Go for a rubber fin with heels. Should you decide to wear booties, take a bigger fin, but keep booties small. The bigger the fin, the more power (up to a point). Avoid fluoro colours, because fish don't like them. Blue and black are best.
Fins should be flexible, not stiff. They should act like the fins of a fish. The fin must spring back after bending. Many plastic fins don't do this. Avoid these. Also avoid jet fins, split fins and very long fins. I've done extensive tests to prove that these do not provide more propulsion for less effort.

Fins should be angled. From your foot they should not point straight forward but bend down. When you stretch your leg, the flipper should point in the direction of your leg, not your foot.

At the moment, the shops are awash with useless fins, and very costly too! The salesmen are always keen to tell you that the latest fad makes all others obsolete, and what I have written is madness. Ask them how deep they free-dive.

Some people are confused about what fins should do. Large fins for instance allow you to swim faster, but at a considerable expense of energy. For snorkelling under water, the only thing that counts is how far can they take you on a single breath in the pool? Fins must provide efficient propulsion: the most distance for the least effort.


The dive suit

Cold is a bad way to lose energy. Your heart and breathing rates go up. You can't hold your breath for long. Besides, you'll feel uncomfortable. Therefore you must wear a wetsuit. Most people think that a thin wetsuit is enough, because snorkelling is more energetic than diving. This is a mistake. A snorkel diver tries to spend as little energy as possible. He must stay as warm as possible.

In New Zealand your neoprene suit needs to be 3 to 5 mm thick. You need to have a hood as well, because much heat is lost through your head and neck. The 'parka' wetsuit with a fixed hood is a good choice but a loose hood is equally effective when tucked in under the wetsuit. Avoid fluoro colours. They scare the fish with every move you make. The thinner your suit, the easier it is to control your buoyancy. Sometimes it pays to have two wetsuits, one for summer and one for when the water is colder. Advanced snorkeldivers prefer wetsuits with smooth outer skins, and indeed this reduces friction.

The weight belt

The weight belt is the most critical bit of equipment because too much weight is right-out dangerous, whereas too little weight prevents you from staying down. The belt must have the right weight for YOU. That depends on the thickness of your suit and how heavy your bones are and how big your chest. You have to find the right weight by trial and error. Your instructor helps you with your first guess.

Repeat these steps while adding more weights until your weight is right.

If you are not using a wetsuit, you may still need a weight or two, depending on your natural weight. Go through the above procedure to check it out.

In the pool or in shallow water, you can practise the ditching of your belt, as would be necessary in case of emergency. Weightbelts release their buckle when the loose end is pulled outward.

To put your weightbelt on, let gravity do the work for you. Always take the belt by its open end, rather than the buckle. In this manner the weights cannot slide off. Roll your back into it while gravity holds the other end down.

When the belt is not in use, always lock it so that weights cannot slide off. It is also easier to transport a closed belt.

Swimming with flippers

At this stage I don't really want you to do much swimming because that uses up a lot of oxygen in your body. Yet you should become familiar with your mask and flippers. So just play around until you feel happy with the mask on your face, breathing through your mouth and swimming with the flippers.

There are two ways of swimming with flippers. One is the 'dolphin' stroke by which the two flippers move in the same direction, and the other is the 'flutter kick' with flippers moving in opposite directions (like when swimming freestroke). The dolphin stroke is very efficient under water but difficult to master. Most divers use the flutter kick.

The flutter kick is not like riding a bike. Keep your legs almost straight but with the least amount of effort (to preserve energy). You will find them flexing a little, just like your flippers do. Most of the action comes from your hips. Should you study the flow of bubbles over someone's fins, you should see these bubbles jetting backward, not downward.

Avoid using your arms. Fish hate arm movements. You'll learn later how and when to use your arms. Learn to relax all the muscles that have nothing to do with your kick. Your arms, and body should be relaxed. Keep your arms alongside your body, or fold them over your back.

f026437: a snorkeller face to face with a large bull NZ fur seal (Arctocephalus forsteri)
f035011: swimming with seal pups is so much fun as they are so agile and cute.


Going down and staying down

The instructor will place a heavy object in the pool, such as a spare weight belt (don't drop lead weights because they damage the pool!!!). The pool should not be over 2m deep here so you won't need to 'pop' your ears yet. You can also use the pool's ladder. In the sea we use natural rocks and strong seaweeds to hold on to. The idea is to learn to go down with the least amount of effort. I don't want you to swim yet. So just learn to shoot down and to grab the heavy object.
quietly following a lazy school of blue maomao
f023317: quietly following a lazy school of blue maomao and trevally.
snorkelling with dolphins is an experience of a lifetime
f034311: snorkelling with dolphins is one of the most exciting experiences of a lifetime.


How deep can you go and how long can you stay?

The minute you have learnt to compensate your ears, you can go deeper than your ability to hold your breath. When you can 'crawl' along a rock face or down an anchor rope, avoiding oxygen consumption by your big leg muscles, you can go down further than by swimming only. You can go further still by using both arms and legs, and consuming the oxygen stored in both. The next limit is where your lungs get compressed so much that your belly's diaphragm starts to hurt. Only people with very flexible chests (like women) can go deeper. For most of us 25-30m is the depth limit. The main limit is your ability to hold your breath while swimming and we'll come to that now.

You should be aware of the risk of blacking out under water (becoming unconscious), which is almost certainly fatal. You need to understand that we have a rather curious method for controlling our breathing. One would have thought that nature measures the oxygen level in our blood, and urges us to breathe when this falls below an acceptable level, but this is not so. Instead, our body measures the carbon dioxide level to urge us to breathe. As we use up oxygen, the carbon dioxide level goes up at the same rate, so there should be no reason for concern.

However, one can suppress the urge to breathe by washing the carbon dioxide out of our blood. It is done by taking quick and deep breaths until one begins to feel dizzy, which is called hyperventilating. By doing this, one can hold one's breath for much longer than without, but as the urge to breathe is postponed, the body may run out of oxygen, which shuts off our brains, causing one to faint. All snorkel divers use this method to some degree, but it is important to know when it becomes unsafe. It is unsafe when you've had a long rest, and your body is at rest. Now it is just too easy to hyperventilate over the safe limit. In this situation 4-5 deep breaths is all you should ever do.

When you are snorkelling actively, the situation is entirely different. Your body uses a lot of oxygen and produces an equal amount of carbon dioxide. Taking deep breaths is necessary to just catch up, and there exists a much reduced risk of overventilating.

There is a slight but important difference in how you take your deep breaths for storing oxygen while not washing out carbon dioxide to excess. It is done by taking a deep breath, followed by a wait of several seconds, a quick refill (breathing out and in quickly), then holding again. This method is more effective and safer than just breathing quickly.

Finally, there exists a risk with deep diving, manifesting itself when going up, just before reaching the surface. As you dive down with full lungs, the air in your lungs becomes compressed, enhancing oxygen uptake in the blood. But during ascent, when your lungs expand, they demand gases from the blood, including the last bit of oxygen. As a result, oxygen levels drop suddenly just before reaching the surface, which could lead to shallow water fainting. This is what your buddy should be watching, as he can pull you to the surface. Experienced snorkel divers who tempt their boundaries, ascend with face up (so you get turned on your back at the surface), fully alert to that prickling feeling in one's skin that arrives just prior to fainting. One hand at the weightbelt's safety buckle to be able to ditch the weightbelt before fainting.

My advice is not to tempt your boundaries until you are very experienced and have a buddy at hand who knows what you are up to. In all cases, listen to what your body is telling you - all the time: fatigue, cold, cramps, headache, snot, dizziness, nausea and so on.

An important secret, seldom told, is that the first dip (dive down) of any day, is terrible, even for experienced snorkel divers. But after a few dips, your body appears to adjust, and it goes better. Eventually it even feels somewhat pleasant. You always need 10-15 dips before settling in. Most people don't know this and they think they can't do it. So never give up before your first 15 dips.

What is that headache and neck cramp? Scuba divers can easily come up with a headache and the beginning of neck cramp, symptoms all too similar to those of migraine. And a migraine it is, caused by chronic carbon dioxide poisoning. Yes, high carbon dioxide levels in the blood to the brain, causes migraines. For migraine sufferers it is caused by brain arteries clamming up (constricting), thereby reducing the blood flow and increasing CO2 levels. In divers it is caused by skip-breathing to conserve air. I've been studying this phenomenon for many years, and here are some tips that work:

f026435: snorkelling in cold temperate waters requires a thick wetsuit and heavy weightbelt. Here a freediver is swimming through a forest of broad bullkelp (Durvillea willana) 
f027122: a snorkeldiver in cold water ducks under floating bullkelp (Durvillea antarctica)


Swimming under water

When you swim under water, your oxygen consumption goes up considerably. It takes a lot of practice to learn to swim efficiently (the most distance for the least amount of effort) but as long as you've learnt to relax your body while swimming, you're half way there. Your muscles are able to do some work without oxygen (anaerobic) before switching to aerobic action and using up oxygen. They have a kind of energy reservoir. This reservoir needs to be replenished each time on the surface and fit people can do so much more quickly than unfit ones. People who smoke take even longer.

!! So the main difference between fit and unfit snorkeldivers exists in how soon the next dip can be done after the previous one. Not in how deep one can go and not even much in how long one can stay under. Unfit divers just need longer to 'tank up' at the surface!

You will understand now that it is advantageous to use as many muscles (hands and legs) to take advantage of the anaerobic energy reservoir, hence the use of our hands to pull ourselves forward. But while swimming under water, most energy comes from the legs only. It is a bit awkward to use your hands without interrupting the steady movement of your body. So we swim with our legs only. Try to make slow steady, 'lazy' kicks. Look and feel how the water flows around your own body and that of others. Look how the bubbles flow around your flippers and those of others. check whether your body is horizontal, perfectly balanced.

Once you've duck-dived down, you will let some air out to balance yourself. If you don't do this, you will spend energy in swimming down all the time, rather than swimming purely forward.

You have now learnt my new snorkel method. Keep working at it until you feel you can stay down as long as you can hold your breath in class. The instructor will repeat all steps, even the breath-hold timing, for each lesson. From here on you'll need to learn a few useful tricks.

Clearing your snorkel

Every time you go down, water will fill up your snorkel and has to be purged. Most snorkeldivers do this by blowing hard into the snorkel. But by saying a loud "Duh", causes a powerful burst of air. But there's an even better way. Just before your snorkel breaks the surface, blow out gently. The bubbles push the water out without any effort at all. When the snorkel breaks the surface, it has no water left in it. It's as simple as that!


Preventing coughs

Salt water in your wind pipe or lungs causes unstoppable coughs. It happens easily when a drop of salt water is inhaled. It can even cause your breathing muscles to clam up so you won't be able to breathe at all. That could last for several minutes, indeed a frightening experience!

To prevent this, hold your tongue in front of your teeth, as if saying "Lll", so that the air has to pass around it. Water droplets are much heavier than air and hit your tongue first. Good snorkeldivers say "Llll" and "Duh" alllll duh time! If you can't clear your snorkel altogether, and you can feel the air bubbling through the water left in it, don't panic! Just breathe in slowly with your tongue in place. Then blow the snorkel clear. This happens often, so get used to it.

Clearing your mask

Water may accumulate in your mask and give you a runny nose. It may get into your eyes and make your eyes burn. A good mask should stay dry but it is very simple to blow it clean. The idea is to replace the water by air from your nose. You can't do it by looking down because your mask, acting as a perfect 'bucket', will hold its water. You have to turn the 'bucket' upside down. So look up for the water to collect under your nose and around your cheeks. Now blow gently into your mask. Air will escape at those low points and push the water out. If it doesn't work well for your mask, use your hand to push the mask gently onto your face, above your eyes. Now the air must escape through the bottom seal around your nose. But always look up! You can do this under water too and experienced snorkeldivers and divers do it regularly


snorkelling amongst reeds in fresh water lake
f037532: snorkeldiver amongst reeds in a clear freshwater lake.
snorkeldiver and algae in a lake
f037432: snorkelling in the green waters of a freshwater lake.
snorkelling over the water weeds in a freshwater lake
f042315: freshwater lakes can provide astounding snorkel opportunities.


Getting in and out of the water

Try to avoid walking on your flippers. That angle in them, which allows you to swim efficiently, prevents you from walking on them. Should you need to walk on flippers, walk backward. In that way they suffer least and it is also much easier. The worst case is walking forward in shallow water. As you move your foot forward, the water bends the flipper underneath, and once your full weight lands on it, you can rip either your tendon or the flipper itself!

To go off a beach, leave your flippers off until you stand chest-deep and sideways towards the waves. Then put them on. Of course you'll put your mask on first. To walk in and out of the surf, use your buddy. Put your arm over his/her shoulder and walk out. In this manner the two of you stand on four feet, which makes all the difference.

To enter the water from a rock. Put your flippers on and go down the rock into the water as far as you can. Squat down and make yourself as low as possible. Wait for a wave that carries you up, then roll down (slide into the water) and away from the rock. Note that divers learn to 'take a big stride forward' to get into the water from a platform. This is okay from boats but is not safe from rocks. You could badly hurt yourself and stamp into sharp sea urchins as well.

!! When entering the sea from a rock, it is important to take your time and to wait for the right wave !! It may even pay to stand half-way in the water!

To exit onto a rock is much more difficult and must be done with care

!! NEVER crawl ashore on your knees. It will just rip your suit and skin and will make you a play ball of the waves. NEVER roll onto the rocks on your belly. It is a sure way to damage the suit and to get washed away by the waves!
freediver and tall seaweeds
f048625: one doesn't need to be very good at snorkelling to go down to 6 metres (20ft) to enjoy swimming through and alongside tall seaweeds.
freediver going through a narrow passage
f023004: even while staying at the surface, one can see and enjoy much of the mysterius underwater world such as caves, gullies, and coves.
freediver and paper nautilus shells
f038535: a freediver finds rare paper nautilus shells no deeper than 5 metres. Only by going down will one be able to make such finds.


The buddy system

If you think that swimming in the sea is safe, then snorkelling in the sea is very much safer because you stay warm, you have very much more swimming power and you can see under water. Yet it is advisable to snorkel with a friend. All snorkel courses I know of, advise one diver to stay at the surface while the other is down. But I've discovered that this is wrong. It is much better to go down together and to come up together. You will enjoy snorkelling much more this way because you will be seeing the same things and can talk about them on the surface. You will also find it easier to stay together. A problem with good snorkeldivers is that they can go much deeper than the 'visibility' of the water. So they will disappear out of sight, to surface at an unexpected place. It is much better to stay together under water.

When you are snorkelling in a class situation and somebody is responsible for you, you must stay close to the instructor. In that way you will also learn more about underwater life. You must tell him if problems arise or when you want to go back. Don't leave your instructor worrying where you are.

Most snorkel courses spend a great deal of time dwelling on aspects of safety but I think that is not entirely warranted. Snorkelling is just swimming but is a lot safer: you are warm and protected in a good wetsuit, you can see where you go with your mask and you are a much more powerful swimmer because of your fins. My many years in the water have taught me that snorkelling is all about enjoyment: enjoying the environment, enjoying the water and weightlessness and enjoying your prowess in what you can do with your own body.

f027604: snorkelling in Pupu springs, one of the clearest waters in the world, is quite an experience.
feeding the long-finned eels in a clear river.
f027514: feeding the long-finned eels in a clear river.


Swell and white water

In the sea there's always some swell about. It washes the water to and fro but near rocks it may result in strong currents, particularly with long, slow waves. In principle, don't fight the water but use its force to propel you where you want to go. When holding on to a rock, it is better to let your body swing around with the swell. That costs the least amount of effort. The fish do it too. When you get sucked into a place you didn't want to go, use the rocks and plants to resist. Then wait for the swell to turn and to push you out again. Waiting is better than swimming.

White water is always unpleasant. Because of the many small bubbles, you can't see under water. That gives an eerie feeling. Use your common sense and swim out. Experienced snorkeldivers dive under because the turmoil of the sea quickly reduces with depth, the 'fog' clears up and you can see where to go to.

One real problem with white water is that it usually races over a shallow spot WITHOUT RETURNING. So it is a one way ticket. It may land you in very unpleasant places. But the biggest problem with white water is that you can drown in it. Because of the many bubbles, the water won't carry you as well as water without bubbles. As a result you will sink deeper into it, possibly not being able to lift your head and snorkel above the white foam. Surfers being caught in a wave with white water, can drown in a similar way. So dive down and swim away from white water.

!! Avoid white water unless you are very experienced.


As you can see, snorkelling well is not very difficult. You have now learnt a technique that will stay with you for life. As you practise it more, it will give you even more enjoyment. Wherever you go in the world, you can always find space in your luggage for a mask, snorkel and fins. And when people commend you on how long you can stay under, remind them that you learnt snorkelling from Floor Anthoni in New Zealand. Good luck and lots of fun!


snorkeldiver and baby trevally (Pseudocaranx dentex )
f050121: these one year young baby trevally (Pseudocaranx dentex ) are very wary of anything bigger than themselves, but after a while they come to trust a patient snorkeldiver. They ae so cute.
snorkeldiver and male sandagers wrasse (Coris sandageri)
f050136: this male sandagers wrasse (Coris sandageri) actually enjoyed being touched, as our relationship with him improved day by day. Snorkelling in a single location has the advantage that the fishes learn to know you.