It's one of the most hostile places on Earth and extends seven miles (11km) below the waves at its deepest point, but the Mariana Trench is full of secrets.
A deepwater exploration mission of the area has spotted beautiful, unknown jellyfish with two types of tentacles as well as a number of other bizarre animals just one week into the study.
The orb-like jellyfish was spotted on a dive at a location named Engima Seamount at a depth of 12,139ft (3,700 metres).