Swimming Underwater — How to Swim Underwater Safely

Underwater swimming is dangerous if you’re not careful. Anytime you are swimming underwater, whether, in a pool or the ocean, you are at risk of drowning.

To help you prevent something catastrophic from happening to you, let’s go over the ground rules for swimming underwater safely.

Swimming Underwater

I’m a fan of looking up to those who push the envelope in a given sport. Therefore, we’re going to look at what spearos, freedivers, and Navy Seals do to efficiently swim underwater. Since this is a fishing site, most of this article will be geared towards better downtimes in the ocean, but the advice still applies to those in a pool.

Let’s dive in and start swimming underwater!

Rules of Thumb for Safely Swimming Underwater

The first thing that you should do when you go spearfishing or freediving is to have a dive buddy. You need to go out with somebody who has more skills than you do.

Spearos typically wear a spearfishing wetsuit when hunting. To counteract the buoyancy of the wetsuit, you’ll need to wear a weight belt around your waist. It’s advisable to have a little less weight in your weight belt than the more advanced freediver because you’ll want to float upwards easier if you get in trouble.

Sacrifice some downtime for safety.

Swimming Underwater Guy

Also, if you start to panic, being light on the weight still should bring you to the surface; but if it doesn’t, let your weight belt go (because buying a new weight belt is better than losing your life).

  1. Never extend a dive too close to your limits. Be aware of your limits. Give yourself enough time to come to the surface. Shallow water blackouts are the leading cause of death for spearos.
  2. Along the same lines as No. 1, always leave enough cushion downtime. In other words, don’t push your limits. If you are a beginning freediver, you should start diving in shallow water (15 feet or less). Then you can slowly work on holding your breath and diving a little bit deeper.
  3. Do your homework before your hunt. If you can, try to get a report from either a website or other divers as to conditions. If the visibility is poor, I don’t recommend going out because it could become a hazard. By the same token, if the surf is too big, you could get thrown against the rocks and possibly hurt yourself or lose your gear.
  4. No fish or record is worth dying for. If the fish that you have speared is in deeper water than you can dive, then either have somebody who can dive that depth help you or put a scuba gear on and retrieve the fish. Under no circumstances should you ever dive deeper than you know you are capable of diving.
  5. Never ever point a loaded speargun at anyone. Being underwater is a novel experience to new divers and can throw off your judgment. Always keep the safety on until you get into the hunting area. Most spearguns that are purchased are sold with “safety’s” on the speargun. I recommend beginners to keep the safety on until you get into the area where you are going to be hunting the fish.
  6. Avoid playful sea lions and other marine animals. Avoid playful sea lions because if you have fish on your fish stringer, then the seal may want to take your fish and could accidentally bite you.
  7. If you are spearfishing in areas known to have sharks, you should bring each fish back to the boat or back to the beach before continuing.

Underwater Swimming Gear

Here is the basic gear you’ll need for swimming underwater:

  • Swimming underwater in the pool: Swimsuit or speedo for those more adventurous.
  • Swimming underwater in the ocean: Swimsuit or wetsuit.
  • Spearfishing in the ocean: Wetsuit, weight belt, fins, fin socks, snorkel, and mask.

Since these items are standard we’ll skip the in-depth coverage of them and focus on items that are more critical for safety in the ocean.

Dive Knife

Everyone going in the water to spearfish should have a dive knife. Preferably more than one and in different locations for easy access.

You should wear the dive knife in a place that you can grab it with either hand. If the knife is on your leg, it can be grabbed with either hand, but if your leg gets tangled in the kelp, having one on your waist or arm will help set you free.

Dive Knife
You can’t go wrong with one or two solid dive knives.

If the knife is worn on your right arm, and if your left arm gets wrapped in some kelp or line, then you can’t reach your knife. The same goes if you put it on your left arm. This is why it’s not always recommended that you only wear a knife on your arms.

A great place to keep a knife is on your weight belt. This way, you can reach it with either hand.

The reason why you want to be able to reach your knife with either hand is: The quicker you can get to the knife, the quicker you can save your life. The reason you want your knife handy and do not want to be fumbling around for your knife is you only have a matter of seconds before you run out of breath.

Some wetsuits that you can order have a knife pocket in the wetsuit (on the thigh). From there, you should be able to reach it from either hand.

Divers will have their preference as to where they wish to wear their knives. It’s a personal decision, and you should wear it wherever YOU think you can pull it out the quickest with either hand.

Dive Flags

Dive Flag
Stay safe by letting boaters know that you’re diving with a flag.

If you are diving off of a boat, you should fly a dive flag (20 inches by 24 inches). The flag needs to be displayed where it is visible so that the flag is not obstructed by anybody’s view. Any vessel that is approaching the boat with a dive flag flying should make a reasonable effort to stay at least 300 feet from the diver’s down flag. This includes all waters other than rivers, inlets or navigation channels.

What is Buzzing?

Buzzing” a dive flag has been added to the description of what is known as “reckless operation of a vessel,” which is a first-degree misdemeanor, punishable by a fine of up to $1,000 and/or up to six months in jail. Buzzing is defined as operating a boat at a reckless speed too close to the boat where the dive flag is displayed.

When entering the water, you should have a dive flag on your float, attached to your floatline. There are 50-foot, 75-foot, and 100-foot floatlines.

A 50-foot floatline has your float and your dive flag 50 feet from where you are diving. A 75-foot floatline has your float and your dive flag 75 feet from where you are diving. A 100-foot floatline has your float and your dive flag 100 feet from where you are diving.

Most floats that are sold have flags that you can attach to them.

With the float and your flag being further away from you, according to the dive flag rules, the boat should stay at least 300 feet from your float with the flag on it.

When diving from the beach, you should bring a float with a flag out with you. If you can’t swim underwater through the kelp with it, you should be able to just tie it to the kelp and keep it close to where you are diving. That way, if there are any boats in the area, at least they know there is a diver in the water.

There are some spearfishing manufacturers that sell a carrot dive float that has a flag attached to it, so that you can pull your floatline and flag through the kelp.

It is recommended not to dive into high boat traffic areas (i.e., Catalina Island on the weekends in the summertime). Most boat owners don’t even know what a dive flag means (or they don’t care).

When you are diving down from 20- to 50-feet, and you hear a boat approaching you, sometimes you can’t tell how close the boat is. So, it is a good idea to come up with your speargun pointed up first, in the hopes that the boat will see you. Every time you come up from your dive, you should look around and be aware of boats traveling your direction. Try to always be aware of where the boats are.

If you are on the surface and you see a boat approaching you, wave your speargun and holler at the boat. Hopefully, the person driving the boat will see you and veer off so that he or she doesn’t hit you. If for some reason you are ever in a situation where a boat doesn’t see you and is coming at you, you should try and dive as deep as you can so the boat doesn’t hit you.

In the past, I have had boats that didn’t see me. In more than one instance, I had to dive under boats, but on one occasion, the boat ran over my floatline and the propeller cut my floatline, but didn’t harm me. The boat just kept going and the driver of the boat never knew what he did. Moral of the story: Always be aware. -Al

How to Swim Underwater

YouTube video

It helps to know how to freestyle swim for effective swimming underwater. One of the best resources for learning regular swimming is the Immersion Swimming Technique. This technique shows you how to be efficient in the water so that you use the least amount of energy to get from point A to point B.

For a spearo, a large majority of your swimming underwater will be on the surface. This is the time you are looking for fish or their shadows to know it’s a good spot to dive. Once you’re ready to dive, it’s important to remember that fish can sense you, so if you’re not quiet they will be spooked.

At the surface take a few deep breaths to load your body with oxygen. Now you’re ready to dive.

Steps for Diving Underwater Effectively:

  1. One your last inhale
  2. Hold your breath
  3. Tuck your chin
  4. Throw one of your legs back into the air as smooth as possible
  5. Then dive down towards the seafloor

Now that you are underwater, it’s time to go swimming underwater. There is a calmness you’ll feel as you start using your fins to propel you through the mid-water-level zone of the ocean. It almost feels like you’re weightless and flying through a mystical land.

Remember, the more you kick, the more resources you’re using and once out, you’ll need to come up for air. Always leave yourself plenty of time to get back to surface on your breath.

Swimming Underwater in a Pool

It’s always important to practice your swimming underwater pool technique before your first ocean dive. The ocean has more variables that can get you in trouble, whereas, a pool is calmer.

If you find that your downtime is poor in the ocean, then head to a pool for practice. As always, make sure there is someone there to keep an eye on you when you do any kind of holding your breath underwater.

A good method of practice is to keep swimming underwater from one end of the pool to the other.

To keep yourself from getting tired, make sure you are streamlining swimming underwater as much as possible to reduce your drag.

You’re going to want to use your feet for the majority of the propulsion. Many people use dolphin kick after pushing off the wall to get at least half of the pool length before using their arms. You’ll know you’re comfortable underwater when you can get from one side of the pool to the other by simply pushing off and dolphin kick the whole way without the use of your arms.

If you have your freediving fins with you, it doesn’t hurt to bring them to the pool to help you practice your swimming underwater technique. It could also be a good idea to bring your mask and snorkel to get the full experience.

In fact, let’s take a look at how to properly snorkel underwater.

How to Snorkel Underwater

YouTube video
  1. Make sure the snorkel is pointing straight up and out of the water. Lay with your face straight down. If it’s pointing too far forward or backward, you might get water in the snorkel.
  2. When diving underwater with a breathing tube (snorkel), it’s important to take it out of your mouth before you start your dive. This helps prevent some water from entering the snorkel on your final breath, which can throw off your rhythm.
  3. Before you dive down and swim underwater, get as relaxed as possible. That means if you’re in the pool, lying on your back out of the pool while finding your zen then rolling over into the water and diving down. If you’re in the ocean, just float on the surface breathing out of your snorkel with minimal kicking and try to relax as best as possible.
  4. When you dive down into the pool use your arms to pull your head down before you start using your feet to kick. If you’re in the ocean throwing one fin back while swan diving towards the ocean floor will get you to sink down since you have a weight belt. Tuck your chin before your head goes into the water to try and get as vertical as possible.
  5. Use your legs for the majority of the thrust. Your arms can be used for fine-tuning your turning, but basically, wherever your head is pointing, you’ll go. Your hands are better utilized for pushing away kelp and holding your speargun.
  6. Come up for air when you feel you’re running out. Make sure you give yourself enough time to make it to the surface without a struggle.

Navy Seals: Learn From the Experts

When learning anything, it helps to pull from the knowledge of the best in the field. Freedivers are a great bunch to learn from, but so are the Navy Seals who have to face some of the hardest situations while being in the water.

One common question that’s asked is: How long can Navy Seals hold their breath?

It’s not uncommon for a Navy Seal to be able to hold their breath underwater for two to three minutes, if not longer.

The world record holder for underwater breath-holding goes to German freediver Tom Sietas, who was able to hold his breath underwater for 22 minutes and 22 seconds.  The difference between a Navy Seal and a freediver is that Navy Seals tend to be in high-energy exertion situations while holding their breath.

Navy Seal Underwater

Navy Seals are one of the most lethal forces in the water. What’s the secret to staying in the water for a long period of time without over-exerting yourself?

Stay calm.

If you talk to a Navy Seal or watch them on YouTube, you’ll see that they are effortless in their ability to move through the water. They have found their flow state and are not bothered by the little things. This is where you need to get your mind if you want to be able to go with holding your breath for a long time underwater.

You need to have practiced enough to be comfortable in your surroundings. This should happen relatively quickly in a pool, but it will take time in the ocean. The ocean has a lot more stimulus to be aware of…it’s the great unknown.

Navy Seal Breath Holding

If you’re having trouble holding your breath while swimming underwater and you are physically fit and have proper technique, then it could be more in your head. If you are preparing to go through BUD/s training, you can try a trick to help you get across the full 50-meter with underwater swimming.

The trick is to dive as deep as you can and swim underwater along the bottom of the pool. By the time you begin your ascend, your mind will think it’s going to be getting oxygen and allow you to go a bit further. Also when you know you’re able to reach the end, start to breathe out slowly through your nose, this will also buy you mental time.

Don’t flop around like a madman or woman. That will just make you run out of energy quickly. Focus on staying calm and being efficient.

REMEMBER: Never do breath-holding practice in the pool without a buddy or lifeguard watching you. It’s not the same as having them there, they need to be aware of what you are doing and watching you the entire time!

People Swimming Underwater

YouTube video

If you still need some visualizations of people swimming underwater, then YouTube is a great resource to watch proper underwater swimming techniques. It’s important to watch as many videos as you can to help you build a model of what you need to do while in the pool.

A handy swimming underwater technique is to find a few videos and then bring your phone to the edge of the pool (make sure it’s waterproof or has a waterproof case), then watch the video and practice. This will help you see the various subtleties that you might have forgotten after watching it at home.

Please also note that it’s not recommended for kids to go swimming underwater without parental supervision.

Underwater Workout

Swimming underwater and diving is a workouts in themselves, but if you find them to be boring and still want to increase your heart rate and conditioning, pool workouts could be a great option.

Big wave surfer Laird Hamilton recommends a few different underwater workouts to help you feel strong and comfortable in the water. All you need is a pool and some 10-20 pound dumbbells.

Treading Drills

Laird recommends you warm up by jumping in the pool and treading water for as long as you can manage. If you’ve never treaded water, then shoot for 30 seconds, but gradually build yourself up to 10 minutes. Laird makes it more complicated by saying that you should hold close one nostril at a time for 10 breaths, then after those 20 seconds are complete, tread water with only your arms for 10 breaths, and finally end with 10 breaths using only your legs. Repeat this as many times as possible.

The Cell Phone

The Cell Phone workout is a brutal one. Grab a 10-pound dumbbell or whatever weight is manageable for your abilities and hold it in one hand above your head. Now use your other hand to swim yourself across the length of the pool. After you get to the end, switch hands and go back across.

To make it more difficult, keep the weight by your chest and swim underwater across the length of the pool, only coming up for air when necessary. Eventually, you’ll get strong enough to make it across the length of the pool without coming up for air.

NOTE: Anytime you plan to swim underwater for a long duration, make sure a Lifeguard is watching you.

The Seahorse

The Seahorse is another brutal workout where you put a 10-20 pound dumbbell between your thighs and use your arms to pull you across the length of the pool. Do as many laps as possible or wait until your abs give out.

Work up to this one by becoming proficient at The Cell Phone.

NOTE: Anytime you’re going to swim underwater for a long duration, make sure a Lifeguard is watching you.

The Ammo Box

The Ammo Box is popular in Hawaii where divers dive to the ocean floor, pick up a rock and run across as far as possible before coming up for air. This version, however, uses a dumbbell close to your chest and you swim across without coming up for air.

If you sink to the bottom, push off and keep swimming underwater at mid-water level.

NOTE: Anytime you’re underwater for a long duration, make sure a Lifeguard is watching you.

How Many Calories Does Swimming Burn?

Calories burned Scuba DivingThe recent estimates by PADI state that an average shore-dive in Temperate Regions (10°-21°C, 50-69.8° F) burns up to 600 calories per hour, which is comparable to jogging. If the water is warmer, say 70-80° F, your body doesn’t need to burn as many calories to keep your core warm so it’ll reduce your calories burned to around 300 calories per hour. Many factors go into calories burned based on your metabolic condition.
Leisurely Swimming Calories BurnedThe Harvard Medical School estimates that a person will burn between 180 to 266 calories every thirty minutes depending on how much they weigh and their metabolic conditioning.
Calories Burned SnorkelingSnorkeling is similar to leisure swimming because most of the time you are casually looking at the scenery. It’s estimated that snorkeling burns between 250 to 300 calories depending on your weight and metabolic conditions. The added calories burned is due to the extra stress on your body as you dive down from time to time to get a closer look at the reef or animals.


Q: Are fish wet underwater?

That’s the real question…

Let me know if you think fish are wet underwater in the comments below.

Jon Stenstrom
Founder & Angler
Jon Stenstrom is a fishing enthusiast. He has over 25 years of fishing experience, and 6 years of spearfishing experience, and is currently learning how to boat. Jon has his Open Water PADI Certification and FII Freediver Level 1 Certification. Jon has traveled the world to fish and dive, most notably in the Great Barrier Reef, Baja Mexico, Thailand, and Malaysia. More Articles
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Articles » Diving » Swimming Underwater — How to Swim Underwater Safely