Deep Blue

 Hatchetfish

Swims along the middle of the screen, towards the Kani Cove exit

Sometimes Visible

 Frogfish

Swims near the Crystal reef exit

sometimes visible

 Oarfish

Appears in the hole in the rocks at the top right hand corner of the screen

Sometimes Visible

 Gulper eel

Swims out from the bottom left hand corner of the screen

Sometimes Visible

 Fangtooth

Swims out from the bottom right hand side of the screen

Sometimes Visible

 Viperfish

Swims along the bottom towards the rock archway

Sometimes visible

 Giant Squid

Can be seen swimming in the distance appearing from behind the Kani Cove exit

Sometimes Visible

 Anglerfish

Swims in the archway near the bottom

Sometimes Visible

 Coelacanth

Swims at the very top of deep Blue along the entrance to Bahari Bay

Sometimes Visible

 Giant Isopod

Crawls inside the rock arch area

Sometimes visible

Here is the prize for Deep Blue! Here is how it looks: