I'm planning a campaign right now, and I'd like to include an underwater adventure in there somewhere. Lost caves, ghost ships, coral reefs, etc. I'm considering having them sent to a either a collapsed old rig or marine research base. Which corp has resources like that under the sea, and where is it located? Any further details would help too.

Target Wastelands is a good resource for that information, comes complete with rules about deep sea diving including exotic gas mixes, defferent ways of dealing with pressure and some new spells if memory serves. Off hand I think Yametesu is the biggest undersea player, fair chance for Saeder-Krupp and Aztechnology to be down there too. And I think Universal Omnitech too, some other AA megas. I'd really say get the book if you're planning on being serious underwater.

The first corp that comes to mind is Proteus AG, which has a number of large sea-based arcologies (arcobloks? something like that I think...) These include areas both above and below the surface, though I do not believe they stretch all the way to the ocean floor.

I wouldnt put it past Saedur-Krupp to have sea-floor mining facilities or the like.

Why do I keep hearing a singing crab?

-Siege

only way to kill it is special shampoo and a fine comb

So much for the lemon-butter sauce.

-Siege

You need an underwater research facility. Strangely enough, it keeps having massive accidents but keeps getting funding for repairs, maintenance and really odd items. The personnel include an insane Captain with a love for HappyCake Ovens, a cyberzombie scientist, a security officer who sounds like the star of a '70's cop show, and ... well, okay. I want an adventure in Sealab 2021.