Nick Nautilus is the protagonist of In Search of Dr. Riptide. He is a "SNAT" (Secret Naval AgenT). Nick is sent out on the quest to find Dr. Riptide and stop his evil plans to take over the world's oceans. Nick is armed only with a small submarine and a JASON submersible. Despite the dangers he faces in his mission, Nick is determined to stop Dr. Riptide.
Nick's submarine is the main vehicle used throughout the entire game (although the JASON submersible must be used at times). It does not have a specific name. The submarine is very small yet maneuverable, with space allowing only one person to be inside it.
The submarine operated by Nick is armed with two cannons, one of which fires upwards. The submarine can fire various torpedoes of varying powers, although the upward cannon only fires one kind of torpedo. The upward cannon is only a feature in the registered version of the game, where the presence of certain new enemies makes an upward cannon more important.
- Nick's last name is a kind of sea creature.
- Part of the text in the ordering information in the shareware version mentions that Nick's new sub can shoot upwards, meaning the submarine used by Nick in the registered version is different or upgraded from the one in the shareware version.
- There are some inconsistencies in the submarine graphics. In the front and rear view sprites, the submarine's height is 1 pixel shorter. In the side view sprites used for the destroyed animation (EGODIE2.L), the submarine is 2 pixels longer than in the other side views (SUBL.L and SUBR.L).
- The upward cannon was added to the submarine in the registered release. However, only the side view sprites (SUBL.L and SUBR.L) were updated. The other sprite animation files for the submarine--TURN.L, BACKSUB.L, EGODIE2.L, and GOTCHA.L--are the same ones from the shareware release. This causes the upward cannon to vanish from the submarine while these animations play.