Really -- and I know I'm bending the rules here -- I'm lookin' for a nice combo of the two. A beach with an ocean full of pool water would be awesome.
Pools, for the most part, are boringly shaped, overly calm, and leave one few options other than swimming redundant laps or floating pointlessly along, face down in the water, until someone breaks the hypno-tiled reverie with a well-placed cannonball.
The beach, OTOH, has got awesome waves to ride and fun riptides to battle, but tastes terrible when accidentally and repeatedly ingested (as it always is). Plus there are things in it with huge, nasty, pointy teeth.
If I could ride waves of chlorinated, unsalted, relatively shark-free water, however, I'd be one stoked beach-goer. Sandy sandwiches or no.
Oh, and we'd have to get rid of the sun too. I've got Dutch-Irish-Russian skin and very nearly burst into flame whenever I go outside during the day.
So, yeah. Chlorinated, unpopulated beach.
At night.
With a diving board.
:>)