How would the world be different if ice were more dense than water

It would alter ecosystems.

Explanation:

If ice were to sink and liquid water were to float on top of ice, then that means that all ice would deposit at the bottom of the ocean. This means that the temperatures of all oceans would be reduced significantly. If this is the case, then marine biology would look very different than it normally looks today. Also, because there is a theory that life originated from microorganims in underwater volcanoes, we have to realize that It would have made life much more complex.

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