I have big friends who won't go swimming because they're too embarrassed about it. I feel that's such a shame, because actually people should be encouraging fat people who are exercising to do it, not pointing and laughing.
My preference is swimming in the sea. I find the sea is more liberating, wild and good fun rather than plodding up and down a pool.
I swam at school a lot. Long-distance swimming in pools, and diving, then when we moved to Hastings when I was 13 I used to swim in the sea all the time; I loved it out of season and when it was rough.