Less than 5ºC -

- in the water - warmer than the air.  Our normal Friday morning routine is a longish swim in wetsuits,  return to the jetty, remove the wetsuit then go out again for a shorter swim. 

Here is A, having taken off her wetsuit contemplating the less than 5ºC water.  Probably 4.8.  She has a rash vest on although I'm not sure that makes much difference. I don't wear one but but I've probably got more natural insulation than she has.
Then into the changing rooms for a lovely hot shower. Followed by a hot breakfast. Perfect start to the day