Terms

Open water swimming is swimming in natural bodies of water (lake, sea, river), as opposed to swimming in a pool. It's a standard part of triathlon and also a separate competitive discipline.

A stroke is one complete arm movement in the water, from entry to exit. The number of strokes per pool length (usually 25 or 50 m) is a basic indicator of swimming technique efficiency.

SWOLF (swim + golf) is a swimming efficiency metric: the time in seconds per pool length plus the number of strokes over the same segment. As in golf, the lower the total number, the better.

A wetsuit is a neoprene suit for swimming in cold open water that retains body heat and additionally increases buoyancy, helping to maintain a more horizontal and streamlined position in the water.