That just gave me an idea of circular swimming pool.
But swimming in lakes is more fun and better for your technique.
If I had to guess, I'd say not as much b/c of the size of the fish.
Edit: Looked into them, they're pretty cool. You can option them with a mirror on the bottom to do form work, they take up far less space than a real pool and the fastest can sustain a pace of 51s/100yard which is very very quick.