Lagunicus is the final planet that you visit in Jazz Jackrabbit 1.
A good portion of these levels takes place underwater. When Jazz splashes down and swims deeper into the water, it gets darker. However: the sea life gives a bit of light so Jazz knows the direction he has to take. Using TNT might help as well.
Octogoons, Octobosses and Bloaty Fishes are guarding the mighty sea and with Jazz swimming into the darkness it might cause some trouble.
The guardian of Lagunicus is Devan Shell in a Orbmarine.
The planet Lagunicus is located in the Triangulum Galaxy.