:O That's a good question...
Kinda a grey area in your question...ice is most dense around 4 degrees...would solid ice being more dense than water also imply that 1 DEGREE water would be more dense than 4 degree water? This would have some pretty massive implications on the heat transfer system on earth, possibly giving a very thin zone between an overtly warm equator and from poles thats actually usable for life. ???? o.o idek
life could certainly be possible as there are plenty of places on earth that never experience subzero temperatures, and therefore never deal with this problem. But more to the point, what would happen to fish in lakes that freeze? Well, because ice is less dense than water, it stays at the top of the lake and acts as an insulating barrier, allowing a layer of ice several feet thick to form over a lake and allowing fish to survive in the water below. If the ice sank, many more lakes would freeze all the way through in the winter killing fish. It would destroy ecosystems in some parts of the world, but wouldn't make all life extinct. Just much more difficult.
then wouldn't ice be at the bottom of the ocean instead of floating on top of the water?
tso those are called glaciers.... ice already floats .-.
there would be no no north and south pole and all the animals that live there - seals, walruses, penguins - would have to live in a warmer climate, or not even exist at all
ice already floats because ice is less dense than water it if was more dense than water, then ice would sink :P