So that I can take a look underwater, make sure there are no reefs or wrecks to run into or huge animals following me?

Location: A flooded and ruined temple complex, looking a bit like a mix of old Venice, R'lyeh and the catacombs of Rome. Scenario: A group of people have gone to the ruins to search for valuable objects, but some have returned empty-handed and some have not returned at all. You are to go there to pick up as many of the valuable objects as you can and save whoever needs saving (and is not yet beyond saving). There are a few monsters roaming around the temple ruins. Avoid them when possible, shoot them onl...

Mission: Pick up some kind of eldritch item from a smuggler in a lagoon village. The smuggler will only meet under cover of darkness, so you will have to cross the lagoon at night. The lagoon is not a safe place at night. It's a kelp forest and there are big creatures on the hunt in there that you should try to avoid. The creatures would look mostly like giant frogfish (related to anglerfish, but with more paw-like fins that they can use to walk or climb). Frogfish usually hunt on the sea floor, but thes...

Not far from what passes for civilisation around here, there is a place where ocean currents meet. The currents drag shipwrecks and carcasses into a reef, where they are then forced to the surface. Sometimes they get swept away or succumb to the rot, but there are always enough to replace them, and so there is always something like an island there. Not much of one, but enough to attract inhabitants. A tribe of scavengers has apparently lived there for multiple generations in an ever-shifting encampent of t...

I don't know if you plan to have random events happen during missions, but if you do: The fog thickens, huge jellyfish rise to the surface, and some rise above it, drifting by overhead like clouds trailing deadly tentacles. If random events are not planned, perhaps it could be used as a madness mechanic instead. Of course jellyfish are somewhat transparent, so although they'd distort the view they wouldn't fully obscure it. Still, steering would be a bit more challenging with the distorted view, so if th...