If ice we're, like most other substances, more dense than it's liquid form, what would this mean for bodies of water that freeze in the winter? What would happen to the organisms that live in them?

In the absence of hydrogen bridges, the molecules are no longer bound and are getting closer. In the end, the water molecules are therefore closer to each other in the liquid state (denser) than in the solid state (less dense). If the ice is less dense, it floats. Like the case of icebergs. And this is a good thing because the fauna and the flora of the cold regions will survive in winter since the icebergs float.

If the ice is denser than water, icebergs will sink and the fauna and flora will not survive.