I've often seen kids in inflatables paddling out at Torquay/Paignton far further than is sensible - many old enough to know better. I recall the lifeboat picked three teenagers out of the water here last year after a similar incident. They had lost their paddles and were all in the water attempting to swim for shore when someone spotted them.
I accept that they were only in t-shirts & lying in sea water, but 3 together would retain enough heat to survive - if they chose to*. Bailing out the dinghy would have been a sensible start, but if they were sensible, they wouldn't have been there anyway!
Were they actually out all night?
* Survival largely seems to depend on the desire to survive above all other factors. Just read a few survivors' stories & work out what seperates them from the people who didn't make it.
One of the stories said "drunken revellers", so I assumed they'd tumbled out of the pub late at night and decided that paddling out in a toy dinghy seemed like a good idea, then got picked up the following morning.