wait - Cameron is inside that thing? Why?
As I understand it, he paid for quite a bit of it. He also has done many deep dives in other types of submarines, so he is actually one of the few people qualified for this type of thing.
To be there when it gets where it’s going.
You foot the bill, you enjoy the ride.
Cameron made several trips to the Titanic in a similar submersible. My guess is he simply finds exploring the ocean depths an enjoyable hobby that he can afford. I also suspect he’s got another movie up his sleeve and he’s doing some prep work.