Had a sail a few weeks ago when the big Westerlies were blowing, at Canton Beach, Tuggerah Lakes. It was honking 30-40 knots, really gusty and lumpy, but the worst part was the water was absolutely bloody freezing. Once you fell in it was hard to last much longer as the cold drained the strength out of you.
Probably the wind chill had something to do with this, but sailed a few days later at the beach and even though still cold, it was definitely warmer that the lake. Guess being just inland and not having much ocean influence affects the water temp there.
My wetsuit is an old Peak steamer 2/3. Wore 3mm booties, high ankle type and a Gath helmet but once you fell in (which was inevitable) you froze. Almost had no feeling in the hands by the end.
Don't think any wet suit would have stopped the cold that day. Probably gloves would have helped.