I realised after my HUET Training that very cold water plus shock means death unless you are very lucky e.g. have crashed by a Support Vessel.
Can't recommend HUET as a fun day out BTW.
The concept of Water being dangerous (especially at this time of year) should be drilled into Children.
When I did my North Sea Offshore survival course I was told some people die straight away from Cold Water Shock on immersion, that you have no more than 10 minutes to death in normal...
In retrospect, when I was a Nipper I used to go and cycle out into the Countryside for miles on my own. From memory around 9-10 years old?
No mobile back then, didn't know where I was going except probably around Delamere Forest and never gave an ETA except for obvious one - I'll be back for...