As I noted a few years back:
When I read of "good swimmers" drowning in the ocean, I’m not all that surprised. Even people who know how to swim have usually learned in a swimming pool. Pools have no tides, no rips. Pools have no undertow, no current, and no swells. Pools don’t have waves.
The ocean makes everyone who doesn't respect it into a novice. The ocean pulls, tugs, throws, rolls, and beats. Swimming in the ocean is as complete a physical activity as one may encounter. The ocean is alive with uncontrollable force, it is nature at its most raw; and it can make anyone who doesn’t respect it into another victim.