@sproutsandparsnips you can, sure.
I jsut kinda started swimming, but nowadays there are quite a few clubs and they can introduce you.
The best time of year to start is summer, of course :D it's always hard to walk into the water, I find slow relaxed breathing helps. Some people walk in slowly and adjust slowly, others find it easier to get in and get the difficult bit over with. Some people wear swimming gloves and swimming shoes and honestly they do help.
If you do give it a go, take a flask of hot water/coffee/whatever to take with you, and just stay in a short time. You find that after a certain point you barely feel the cold and if you're starting out then you should stop shortly after that, and build up time in the water slowly.
It really does gradually get a lot easier, though the first rush in is always a challenge!
People who do take to it feel great after though. It can give energy and you're absolutely in the moment, worries fall away and you get a lovely mood lift afterwards. Plus you're in nature and getting fresh air and exercise.