This means that the battery is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours that it supplies are measured. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications.
Pool meets are usually no more than 4 hours, but beach meets last about 7 hours. It depends how many events are in the meet. And then if it is a really big meet (like a tournament kind of) it can last days. Hope that helps.
The Seafair Triathlon is held on the shores of Lake Washington from Seward Park. It features both Sprint - half-mile swim, 12-mile (19 km) bike ride, and 5 km run - and Olympic distances. Participants can compete individually or as a team. Typically, the Seafair Triathlon is held the third weekend of July.