Many years ago I was involved in a week of research into sea survival jointly funded by Plymouth poly and the Coastguard. One of the experiments was to take 30 ish undergrads, brief them on getting into a raft, inflate a raft 2 miles off shore and let them get into teams and try to get in. The only people who managed it were people with previous experience in sailing etc. There was a 100% failure from the untrained and inexperienced. Having watched this I find it very unlikely that your average 50 + overweight PPL with no training would get into a raft unless he as very lucky. I would not expect many to even get it out of an upturned aircraft with a sea running. If you are going to fly the Irish sea either get an immersion suit or go on a ditching course.
Rod1