The other days they cannot make up the sleep they have lost because they must finish the homework they couldn't complete the night before. There is always a Saturday morning practice as well, so the only time a swimmer obtains a decent amount of sleep is Saturday night. Training itself is rigorous and painful, both on the body and on the mind. It involves a demanding combination of dryland exercises and two hours of pool time per training session. These critics cannot be any more wrong.
Swimming requires more thought and focus than many of the common sports others play.
True, you don't contend with a ball, nor do you need to devise strategies and plays involving other people. Resistance through water is a factor that is much more significant than resistance through air, and any little error can add tenths that build up over the course of a race. You must feel where your body is in relationship to the water, and there is always, always something you are doing incorrectly. Swimming becomes an intricate dance of perfecting one thing and discovering another that is flawed. Even the best in the world, the Olympians and world record holders, are forever looking for minute adjustments in their technique to drop mere hundredths from their times.