Ask Stew: How Preparing for Swimming in Open Water Differs from in a Pool

U.S. Navy Petty Officer 2nd Class Mauricio Varonmoncayo swims 2,500 meters in open water at Kin Blue, Okinawa, Japan.
U.S. Navy Petty Officer 2nd Class Mauricio Varonmoncayo swims 2,500 meters in open water during a Scout Swimmers Course at Kin Blue, Okinawa, Japan, March 4, 2019. (Lance Cpl. Kevan Dunlop/U.S. Marine Corps photo)

Swimming in a pool can be very different than in open water, largely depending on the type of open water; swimming in lakes is not the same as doing so in rivers and larger bodies of water. From tides and currents to colder, darker and murkier water, there are many elements to prepare yourself for, both mentally and physically if considering open-water swimming (military or civilian competition).

Here is a great question from a future military member preparing for a job in Navy Special Warfare/Special Ops (SEAL, SWCC, EOD, diver). He is considering entering some open-water competitions prior to joining the service.

In military swimming (with fins) and swimming in general, what are some of the key/major differences in form and breathing when ocean swimming vs. pool swimming? Any major differences I should consider when I start training [in] open water? Thanks, Jim S.

The form of swimming in a pool, versus swimming in the water, changes very little, if any, but you will need to add in a few habits when in open water. For instance, swimming straight in open water is much more difficult than staring at a line at the bottom of the pool and having lane lines to keep you straight. A common technique is to look up every 5-10 strokes for an object in the distance that is lined up with your destination or turn-around point.

If swimming parallel to the shore, guiding by maintaining the same distance from the shore is an option as well, but make sure that the beach is actually straight and not curved or concave in any way.

Tides and Currents

Larger bodies of water/rivers will be affected by tides and currents. In spec ops swimming, the fins you will use are likely the sturdy Rocket or Jet Fins. These fins are built for power to get through some currents -- not necessarily speed, like some of the more flexible slip-on swimming fins are. Getting used to swimming with these bigger fins will require some time getting your ankles mobile enough not to feel the pain.

You will see a big difference in swimming against currents without fins or even with slip-on fins, compared to the bigger scuba fins used in spec ops swimming. Without fins, kicking and pulling harder will be required when going against the current. You can add in some glide time when swimming with the current, however.

Waves and Wind/Bilateral Breathing

Dealing with waves and typically salt water will potentially cause you to inhale a mouthful of water with improperly timed breaths. It is helpful to know the side of the waves and swim with your back to the waves/wind, if possible, to avoid a face full of water during inhalation. Whether you are swimming freestyle or using the combat swimmer stroke (CSS) with fins, learning to breathe on both sides of your body should be a skill practiced in the pool.

Colder, Dark and Murky

Unless you are swimming in Bahama-like water, chances are you may not be able to see much farther than your own hand. This can create an uneasy feeling at first, but you get used to it.

Having a swim buddy is helpful. Having a partner or buddy is always a requirement in military swimming so I would recommend finding a swimming partner, if possible. You may also need a wet suit, depending on water temperature and the duration you are in the open water. For safety, it is best to have a wet suit as you will be more buoyant.

Swimming in a pool or open water is going to be helpful when you start your spec ops selection training. Whether you build up a majority of your miles per week in a pool or open water does not really matter; you will be required to swim in both during training.

But mastering these added skills will keep you within the standards of open-water swims if you learn how to swim straight and work the tides and currents to your favor.

Stew Smith is a former Navy SEAL and fitness author certified as a Strength and Conditioning Specialist (CSCS) with the National Strength and Conditioning Association. Visit his Fitness eBook store if you’re looking to start a workout program to create a healthy lifestyle. Send your fitness questions to

Want to Learn More About Military Life?

Whether you're thinking of joining the military, looking for fitness and basic training tips, or keeping up with military life and benefits, has you covered. Subscribe to to have military news, updates and resources delivered directly to your inbox.

Story Continues
Military Fitness Swimming