Over the course of my life, growing up in Hawaii, surfing and swimming every day, I've spent more time underwater than most. And even I don't feel completely comfortable there. That's because humans have a built-in fear of water, and with good reason: There's no oxygen to breathe! People drown in water. So naturally, it triggers a survival instinct and causes some alarm. But exercising underwater also creates tremendous benefits by challenging your body in ways you can't on dry land.
The underwater workout produces a deep level of exhaustion because it takes more effort to move through water. Water is 800 times as dense as air, so it creates pressure on your body, which increases your blood flow. It's like wearing the tight compression clothing that's become so popular now in sports; athletes like it because it's said to enhance blood flow. When you breathe while most of your body is submerged, the pressure forces your lungs to exhale with greater force because you have to push the air out. And there's even a theory that being underwater enables your lymphatic system to circulate at an optimal rate, doing in 24 hours what in a sedentary person could take three to five days. So spending time in the pool or ocean can help cycle and clean your body.
Pool training can be deceptive because you don't get nearly as sore. The buoyancy of the water counteracts the effects of gravity, so you don't have the same risk of injury you do on the ground, and there's much less impact on your bones and joints. Working out underwater can help make you more flexible and loosen you up.
But you do get superfatigued because of the water resistance. When we train in the pool, almost everyone ends up taking a nap later that afternoon – that's just kind of the rule. You feel a deep tired that you don't equate with muscle soreness but that comes from oxygen restriction and changing your breathing patterns. It's almost like you go into oxygen debt, and it takes a few days to recover. Before you start this kind of training, get a face mask. Being underwater is like being in an unknown, out-of-focus world where you think, "What's here?" Having a way to see clearly will help increase your comfort level significantly. A mask works better than swim goggles because it will cover your nose as well as your eyes, preventing you from inhaling water.
We put guys through paces in a pool with weights – regular dumbbells – nearly every day. I recommend starting any workout by treading water for a few minutes before you use weights. You don't need anything heavy – one 10- or 20-pound dumbbell will do. Follow my workout protocol below.
Four Water Workouts
Warm up by treading water. Do drills: Tread while breathing through your right nostril, covering the left nostril with your left hand. Repeat for a count of 10 deep, slow breaths, in and out, and then switch sides. Then tread using only your arms for 10 breaths, and then using only your legs. Tread while holding your right ankle with your left hand; switch sides.
The Cell Phone
Hold a 10-pound weight with a straight arm over your head and sidestroke to the other end of the pool, as if you're carrying a cellphone you have to keep dry. Switch the weight to the other hand and swim back. Then hold the weight underwater next to your stomach and sidestroke, coming up for air when necessary. As you get stronger, see if you can keep your head out of the water for the entire pool length.
The Sea Horse
Squeeze a 10- or 20-pound dumbbell between your thighs and hold your legs out in front of you, bending forward at the waist so that your body forms a pike, or a V. Use your arms to stay afloat as you move your body across the length of the pool, holding up your legs and keeping your ankles out of the water as much as you can. This means you'll have to support the weight of the dumbbell and your legs with your abs and shoulders. It'll really blow out both and give you a great core workout.
The Ammo Box
Hold a 10- or 20-pound weight against your chest while swimming underwater from one end of the pool to the other. Don't worry if you don't make it to the other end. If you start sinking with the weight, swim as hard as you can. If you hit bottom, use your legs to propel yourself to the surface again.