It's the freezing waters that get you, takes your breath away so it does.
I swam in there a few christmas's ago with me old pal toaster, we were pissed so didn't feel the cold.
Very foolish but it was dark so no-one could see me and my old pal toaster, best time to swim in there is when it's pitch black and theres no-one to help, more of a BUZZ and it won't piss a load of people off