I think it usually works best, especially with the newer luggage issues, to optimize packing by distributing camera gear, dive gear, and clothes in the ways they pack best. Rather than packing by function with camera case, gear bag, etc.
My husband used to use a hardsided Samsonite rollaboard to carryon most of his camera gear. I think it was lighter and more compact than a pelican, and was "uninteresting" looking. But still a problem for small planes, and got to be a real jigsaw puzzle to pack (or repack at security) as the foam he started with gave way to bubble wrap to fit more in. And without the foam, checking it if he had to was no longer a good idea. So he's gone to one of the camera backpacks as his main carry on, plus another slightly smaller backpack as his personal item. Some of the heavy but not fragile items like batteries and strobe arms go in checked luggage or my rollaboard, however works. It's helped reduce weight and worked better for some flights. Flights on some international carriers that won't let you carry on much even on a regular jet are another matter. Have to have different packing schemes depending on the itinerary.
Cayman Airways flies twin otters to Little Cayman. They're bigger than some planes used for interisland hops in the Caribbean, or what used to fly to LC many years ago, but they also hold more passengers. So maybe less of a luggage problem than some planes, but not enough to bail you out.
. My wife does not have an UW camera so possibly we can leave the Pelican case at home and distribute the stuff to minimize baggage. Also, I talked to the LDS about my concerns and the staff, whom had been there before, said that Cayman Airways (the airlines for the trip) used bigger planes than most of the other "puddle jumpers" ????
