I used to get them doing kick sets in the pool and body boarding, I have had them long boarding, usually when inside getting pounded. Swim coaches have told me oxygen, hydration and potassium. Drink lots of water for 2 days before a cramp inducing session, eat your bananas and breath before you need it. I have found that rapid deep breathing can ease a cramp. but here is the best cure...... Tonic Water!!! the quinine in tonic water has some ability to inhibit cramping. I use it regularly now, about 4-6 ounces for a day or 2 before and every day during a several day swell. I mix it with orange juice or just hit it straight up, its kinda gnarliegh but but works.