Do you even make your sims swim? All they can do is swim laps and splash people. There's the jumping platform but that's just a way to get into the pool. I like building pools but they're so borin...
TS2 pools had diving boards with several different animations, whether chickening out or different dive styles. Sims also had multiple swim styles, could float on back, and could swim all over the pool, not just laps. Marco Polo has already been noted.