The ocean is an average of 3.2km deep. Humans know of about 245,000 marine species. The most common sea animals are those without a backbone, such as jellyfish and shrimp.

A sea sponge and sea star on the Retriever seamount, one mile deep in the Atlantic Ocean, July 27, 2021 Courtesy of Christopher Mah/NOAA 2021-07-28T21:56:16Z Share ...