Make sure that whatever you do, you avoid hyperventilating while training in the ocean. Hyperventilation is extremely dangerous because it reduces the urge to breathe. It kills alot of competitive swimmers and free divers.
some big wave surfers claim that sometimes when they know a beating is coming, and they have a little time, they will do something similar to hyperventilating before taking a deep breath. it will increase the oxygen saturation or something like that.