The answer is that a unicellular organism would swell and burst.
In a hypotonic solution <span>the </span>water concentration<span> of the cell's cytoplasm is </span>lower<span> then that of the hypotonic solution. If unicellular organism is exposed to a hypotonic solution, the water from the solution will enter the organism by the process called osmosis. The aim is to balance water concentration on the inside and outside of the organism. But, that water entering the cytoplasm of the cell will make pressure on the cell membrane. If the </span><span>excess water cannot be removed from the organism, it will swell and burst.</span>
It is better for the whales to go where the whales have the ability to dive longer and deeper to find cooler water.