Knapp's Investigation Alien: Light Goes Underwater

[Jack Mallory]

I found this to be fairly illuminating (sorry, I couldn't resist!).
And these stats did quite surprise me.

According to NOAA, scientists estimate that bioluminescence exists in 90 percent of the animals living in the open ocean, in waters below 500 m (1,640 ft).

Bioluminescent Animals Photo Gallery
https://ocean.si.edu/ecosystems/deep-sea/ocean-layers