All I know is that if you can swim well and you want a workout, swim with sweats on, if they let you. The weight and drag the clothes will give you will definitely work you out. My gf use to do that when she was on swim team.
If you can't swim well don't try it. I don't want you drowning. Or just do it in the shallow end.
Yesterday is History, Tomorrow a Mystery, Today is a Gift, Thats why it's called the Present.