Your mother's bellybutton.
No one can determain this because the bottom has still not been found.
Starfish have been known to live as deep as 6000m
Starfish have not become extinct so I am afraid you have been duped.
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Fossils of starfish can be found in various marine sedimentary rock formations around the world, particularly in regions with well-preserved fossil records such as the United States, Germany, and Australia. These fossils are often discovered in ancient coastal areas or seabeds that have been uplifted over time.
NO
The deepest scientist have been able to study earths interior depth is 12,262 meters
No such place has so far been found.
The Puerto Rico Trench, in the North Atlantic, is the deepest, it has recently been measured at 8,742 metres (28,681 ft).
The body cavity in a starfish contains the circulatory system and the haemal system. The body cavity also helps starfish by distributing oxygen that has been distributed throughout the body, through the body.
Yeti crabs have been found at the depth of 7,000 feet. However, as scientists are unable to penetrate the depths of the Mariannas Trench for very long periods, there is still very much more to be found beneath the sea.
A stray animal is any animal which normally found in a certain place has been moved or moved itself to a different place. (Usually a stray animal is one that is not wanted in the new place in which it has now been found.)