Dude needs to fly to Newfoundland and rescue the lost tourist submarine!
I'm absolutely serious about this. A deep-sea submersible carrying tourists to see the wreck of the Titannic is missing, and if anyone is still alive, they're 12,000 feet down.
Deep-sea diving is a small and very expensive world, and Cameron is really into it, he'll dive down to the bottom of the Mariana Trench just for fun! (And maybe a bit if science.) So if anyone on Earth has the money, expertise, and equipment to stage a rescue, it's Cameron!