After you've gotten some swimming lessons (check out the books and technique made by Terry Laughlin - swimming made easy might be a good start), then find an op

After you've gotten some swimming lessons (check out the books and technique made by Terry Laughlin - swimming made easy might be a good start), then find an open water swimming club that takes on beginners (try meetup or facebook). Might not be for you, but you also might not know until you've tried it.