How does anomalous expansion of water help aquatic organisms in cold climate?

Aquatic life is benefited by the anomalous expansion of water because the water freezes top to bottom, not bottom to top. If it froze bottom to top, then the aquatic life would be pushed up, up, up, towards the surface of the water. Since it goes top to bottom, and the water at the bottom remains at 277K, the Aquatic life can survive there.