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.
This is a fun form of exercise. Not only will it tone up your arms, but also the whole body. In a studies, it was proven that women who went for swimming at least 3 days in a week managed to reduce flabby arms in just 9 sessions. Hence, swim swim swim.