A landing in cold waters is for practical purposes non-survivable unless you are wearing an immersion suit
I can vouch for that, having had the good fortune to experience some of the survival training which was carried out at the (former) RAF Mountbatten. We were taken out about six miles into the English Channel - - it was February, and it was snowing - - and we were thrown off the boat !
You might not believe how cosy you can eventually feel in an immersion suit in a single seat life-raft !
Thank God, I've never had to consider ditching for real.