@Tanm2021 20 April 2021 more from that month

Fin whales are recently used to map the ocean bed ir ocean floor. Male fin whales sings bellowing songs to attract their mates. This song is considered to be the loudest sound that a marine creature can make. Because they can be heard 1000km away!! And not only this. It can reach the depths of 2.5 km and it bounces back and give researchers accurate measurement. Before that researchers large airgun or other instrument to measure sea bed.