Yep.
The water off Florida is low 20's and the coast guard helicopter will come get you - but try that 150 miles SE of Antigua - no helicopter is coming even if they know where you are the cutter won't get to you in under a day so you are spending at least one night out there.
Even at 23C exposure is going to get you.
Channel has more ships etc. crossing and laterally you're going to get picked up.
I have been thinking of investing in a survival suit but the hot and sweaty during the flight (my plane is Ok in the air - but 40C+ during the taxi even with the door open and the air scoop) and it making it cumbersome to exit in the event of a water landing puts me off the idea; I do have a SpareAir though and being a diver know how to use it properly.