Clark wrote:

That would be a small helo (Jet Ranger or R-44 size)...

At least double that for GOM ops and a 412 based on some really old
numbers I'm familar with. I'd guess nearly double that again for North
Sea. Even with bigger aircraft it takes at least a couple or three or
four flights to make a crew change.

Those ballpark type numbers would be just for aircraft and crew. There
are some admin/facility/G&A costs on top of that.

The question had come up because we are also divers and we wondered whether
it would be more economical to moor a couple of large barges with
facilities aboard at a particular remote dive site and have the customers
shuttled back and forth via helicopter than it is to currently have the
customers dive from converted crew boats that leave the night before and
arrive on site the next morning. Of course, this would also leave the
option of using a boat for shuttle service or even some sort of open ocean
seaplane like a PBY Catalina or a Grumman Albatross. Although a Cessna
(172, etc) on floats would definitely be economical for a couple of divers
to get there, I suspect that except on the very calmest days, it would not
be acceptable for open ocean sea states.