What do top surfer Kelly Slater and the Orlando Magic’s Aaron Gordon have in common? Their love for underwater workouts.

 Water is 800 times denser than air, so resisting it as you raise weights or do squats gives you a super-intense workout without stressing your joints. Slater runs on the ocean floor carrying rocks to boost lung power and muscle strength; Gordon became a high-leaping dunk king by carrying a huge kettlebell across the bottom of a deep pool.
 Check out these great underwater-exercise videos from Speedo USA, then find yourself a beach or pool—try the local Y—and some kettlebells or dumbbells and hop in. Here, some standouts:

– Split Squat Jump Scissor 
– Horizontal Push-Pull 

– Lateral Lunge 

– Supine Cycling 

There are 70 free videos in total, and Speedo is working with EXOS on a certification program for trainers, which should be available in the coming months.