One trip down the pool.
One or more consecutive lengths. A new interval starts after a rest.
A stroke is counted every time your arm wearing the device completes a full cycle.
Your swolf score is the sum of the time for one pool length and the number of strokes for that length. For example, 30 seconds plus 15 strokes equals a swolf score of 45. For open water swimming, swolf is calculated over 25 meters. Swolf is a measurement of swimming efficiency and, like golf, a lower score is better.