This fitness expert swears by underwater weights workouts - would you try it?

Of all the water sports, surfing appears to be the most laid back. Surfers are well-known for their chilled approach to life, but behind this calm exterior, riding the waves places intense demands on their bodies. 

Laird Hamilton, the world-famous surfer turned fitness expert, knows this better than most. The professional big-wave surfer has long extolled the benefits of underwater weights training (both to get board-ready and beyond), incorporating kit such as the best adjustable dumbbells and the best kettlebells into his pool-based workouts.

In a video recently posted to his Instagram account, Hamilton is seen grabbing a 40-pound dumbbell, and swimming two lengths of a pool underwater, switching the weight between hands for each length. As Colleen Quigley, the American Olympian and long-distance runner, wrote in the comments, "This looks terrifying."

It's not uncommon for questions to go unanswered on Instagram, but when one user asked, "How many sets of these are you doing? Do you do timed interval sets?" Hamilton responded, "[it] can be timed. Go every 45 seconds or 5 breaths on the return and go. Whatever suits your mood."

The underwater workout is also featured in many programs offered by XPT, the training company founded by Hamilton and his wife Gabby Reece, a noted American volleyball player.

These exercises build variety into your workout and force you to adapt to the instability of the water and additional strength required to move the weights. However, the primary motivation behind XPT's underwater weights workouts is to help you control your breath.

Water resistance training is a common component of rehabilitation programs, thanks to the reduced effects of gravity while in the water. However, Hamilton and his team see holding your breath as one of the key benefits, as it forces the body to oxygenate your blood and delays the onset of lactic acid in your muscles.

If you wipe out while riding a wave and fall off your surfboard, the power of the wave is going to keep you underwater for an extended period, and it'll probably be longer than your body feels comfortable with.

You also have your board strapped to your leg, and it'll be getting pulled around while you're below the sea. Hamilton's XPT sessions are designed to get you used to the panic and discomfort of reduced oxygen underwater and develop breathing techniques to help you through the experience.

Fortunately, this isn't the only way to focus on your breath, as grabbing one of the best yoga mats and taking up a regular yoga practice can reduce stress, anxiety, and improve your balance. To develop strength back on solid ground, it's worth learning how to deadlift with dumbbells for board-ready muscle as well.