Question

what happens to marine life when the outside temperatures becomes less than 0°c

Answer 1

When the outside temperature becomes less than 0°C the upper part of the sea or oceans freezes, the lower part is not frozen and its liquid. For instance, if the upper layer is around 0 degrees the lower layer of water will be around 4 degress and since ice is heavier so it floats on top and does not disturb the marine life. So if the outside temperature is dropped, marine life go a bit deeper area of the water and stays alive. 

Answer 2

Answer: When the surface water freezes into ice and expands, it insulates the water which keeps the aquatic/marine life alive.              

p.s. due to the expansion of water, the coverage of the ice is big

Explanation: bruh