[Byron]

My best experience was at night and in wintertime, whilst enjoying a stay at a Spanish hotel with excellent guest facilities. These included an in/out heated pool with a flexible barrier and the "out" allowed a swim under the stars - plus a quick snowball fight in speedos on the deck - and a return to "in" when feeling cold at minus whatever it was.
The fun time was heightened by the participation of some friendly "locals" - whether staff or gatecrashers I know not.