You are far too modest in your alias <vbg> (in edit: meaning you nailed Zeev's question!!), I actually did not know that if ice was denser/heavier than water, life would not be possible. Why is that so, because in the Ice Age there was water in the seas below all the ice, and life survived there...? Whereas if it froze solid, bye bye...?
(Incidentally, I chose my alias because, if I had to write an exam on finance topics, zero is pretty much what I would get!!). And not much better in biology or physics, it looks like...<g>
zerofinance