The Mariner Returns is Issue #1 of 4 in Volume One of the Waterworld: Children of Leviathan comic books.
It was released in August 1997.
The story begins an unspecified amount of time after the Mariner has left Dryland. Since his last trimaran was destroyed by the Smokers, the Mariner has a new one of similar shape but constructed from an old jet fighter.
The Mariner is searching Waterworld for answers as to the nature of his mutation. Whilst searching for salvage among the ruins of Washington, D.C. on the ocean floor, he is attacked by a whalephin. The Mariner spears it with a harpoon in it's blowhole, begrudgingly as he hates to kill any sea life unnecessarily. While going back to the seabed to see if it is still alive, he notices something astonishing - a train car-like submarine operating on it's own power and lighting up the area around it. The Mariner is wary, and decides to head back to the surface.
Aboard the submersible, a group of men and women notice the Mariner ascending, and are astonished that men still live on the surface. They debate either attempting to communicate with the Mariner or avoiding him. Their leader, Richard, says that they should go up and open the hatch, not least of all to breathe 'real air' for once. A woman, Alannah, voices caution that there may be savages up there. Richard ignores her concerns and the submersible then also begins to ascend.
The Mariner resurfaces, and he considers racing away, but keeps within visual distance of the submersible out of curiosity. It surfaces and people emerge, but another vessel suddenly also bears down on the location - a raiding party of Children of Leviathan. The Mariner recognises them and to his relief, the marauders focus on the larger target of the submersible.
to be continued