Skanska camp (1st Eng Camp) on Gargaresh has a 25m open air pool. You need a wetsuit at the moment!
I believe one of the International schools has a covered pool, but haven't managed to get myself invited yet 
LCM camp has a 25m pool , again, open air, unheated.
Go on GoogleEarth and you can see large pools.
There's always the Med. I was swimming off Regatta last week, it was lovely!