The deep seas are home to some absolutely amazing creatures. Among my favourites are the dragonfishes (Stomiidae). Perhaps the most well known of the group is Malacosteus niger, or the stoplight loosejaw (left). As the name suggests, the fish has a red bioluminescent organ under its eye. This is pretty odd, since red light is filtered away by water and basically does not exist in the deep: most deep sea animals can't see red at all, and some of them are bright red as a camouflage - it's the same as being black.
However, the stoplight loosejaw has a red light AND can see red, thanks to a photopigment that is derived from chlorophyll - which is an oddity as well, collected from sinking dead algae by the crustaceans this animal eats. How exactly it manages to catch smallish crustaceans with such a jaw structure, nobody knows. However, we do know how it finds them: with a private flashlight nobody else can see!
The other fish is a related species, Pachystomias microdon or the smalltooth dragonfish. It has an even more complex assortment of lights on it than the stoplight loosejaw. I have no idea what they're all used for.
This was my first attempt at using Procreate on iPad for colouring. Turned out ok, I think.