I grew up swimming in outdoor pools, but they were partly heated, unless they were the kind of pool which is fed directly from sea water (there are a number of pools like this in Australia, typically at the end of a beach.

It's not a university pool — it's this one (link goes to the pool's Twitter account, which has photos of the pool for the icon and banner). It's only open for a few months a year, and is normally packed with recreational swimmers, which makes lap swimming frustrating — so actually at the moment the current set up is ideal for me!