I know im gonna get torn up for this but my carpets LOVE to swim in the pool. i catch some flack because of the chlorine but the general rule is if its ok for people its ok for snakes and ive seen experts like nigel marvin do it. Anyway swiming is great exercise. Mine go right to the bottom of my ten foot pool and swim really fast. Its cool and they love it. My female irian jaya goes crazy for it practically jumping out of my hands to get in. Plus, its a great way to interact with them and really helps tame them. Ive never seen snakes get so excited or appear to enjoy themselves like this.
hope this helps
Jason