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.
During aerobic exercise your body's demand for oxygen can be met and your intensity sustained. Any exercise you can maintain for more than two minutes will be aerobic. Aerobic swims are those that are longer in distance and duration. These swims are performed at an easy to moderate pace. Using the Borg Rating of Perceived Exertion scale, which measures physical intensity for a given effort on a scale of 6 to 20, an aerobic swim would fall somewhere between 7 and 13.