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.
Young or old, fit or not, six weeks seems to be the most common length of time it takes to be able to swim a mile without stopping. It requires swimming three times per week and the willingness to be somewhat uncomfortable while stretching your aerobic capability. This series of swim workouts will get you swimming one mile in six weeks. (Ruth Kazez). You can take some of the recommendations to make your own version of the plan. your main focus is to increase your distance while reducing the number of times you have to stop. Don't try to achieve the mile in the first week or two.