Yes the bottom of the Mariana Trench does contain some sea life and some weird creatures live at the bottom of the Mariana Trench.
As far as what's known to live at the bottom of the Mariana Trench.
The Mariana Trench is home to a lot of sea cucumbers, sea anemones, jellyfish, comb jellyfish, and giant amphipods.
No normal type of fish live there but there is indeed some life down there.