I'm pretty cold-blooded, er--- cold-natured---I tend to get really cold, really easily... but while diving in Cozumel's 80F degree water with no hood, I never got cold... My dives all ran between 48- 87 minutes, 3-4 dives a day...
Now... California diving
Oh... and I had a neoprene strap on my mask in Coz.... and my hair didn't get tangled.