If in doubt, just send the Shadowrunners underwater looking for things that may/may not be 4th World Atlantis

We had a great campaign once with runners on an undersea mining platform that had just stumbled on some ancient artifacts (nothing 4th World in this case, but still incredibly valuable), but was also holding up drilling on an expansive oil well.
Treasure was the remains of a viking longship, with buried warchief (and jewels)
So, several Johnsons had several teams running simultaneously, with conflicting goals:
Team 1) Secure the artifacts, sabotage the rig to hold up drilling (but not destroy)
Team 2) Destroy the artifacts and all evidence of them, get the rig drilling again
Team 3) Secure the artifacts, and destroy the rig
So it was a good cross between SeaQuest DSV, Under Siege and Deep Blue Sea. Fun few sessions....
- Paranoia about using firearms in the undersea environment
- Unknown whether anyone encountered was a civilian miner or an opposing runner-team
- Webs of network security allowed remote control of different map zones (alarms, cameras and in some cases, turrets and bulkheads)
In the end,
Team 3) got some of the artifacts off the rig and set it to blow ,
Team 2) Blew up 3)'s submersible getaway vehicle (with them on board), and disabled the explosives
Team 1) secured the remaining artifacts, removed every fuse and lever in the drilling chamber and got away (With team 3's tracking chip merrily giving away their location at random intervals)
Ahhh, good days...