This is the kind of thing I was looking to replicate
This was my starting point. I had cut the flaps, aileron, and elevators loose and positioned them. I also damaged to aircraft very mildly. I wanted it to be damaged enough to have crashed but whole enough that the pilot could crash-land it. I decided to put a bit hole through the fuel tank, you can see splatter from the fuel leaking out which forced the plane down.
For the base I used a combination of carved insulation foam (something I will never use again) and cast plaster rocks held in place with sculpting putty. There is a deep notch cut out for the left wing. You can see some of the weathering I did on the airplane.
The base was primed grey to take the glue I used to hold the sand on. I used watered down Elmer's white glue brushed on then sprinkled with sifted dust (to make it more fine). The rocks have been painted grey, given a dark grey wash, and dry-brushed light tan and a very light brushing of white.
The plane nestled in it's place, this was a test fit partially through the sand process.
The wing has been locked in with sculpting putty, after this I would finish putting on the sand. Here you can also see the lichen I used for seaweed.
Then there's our intrepid diver. For a base I used a mechanic from a P-61 kit. I sanded down his bulky clothes to look more like a wetsuit and painted it accordingly. The flippers were scratchbuilt from sheet styrene. The goggles were carved from clear sprue and the regulator is a modified 200lb bomb fuse.
The air tank is the business end of a missile topped with part of a helicopter control stick. Thin wire was used as the air hose.
To keep our diver swimming I ran painted, copper wire through holes in his hands, through a "dive weight" and into the insulation foam. The wire was curved into the foam so the diver won't spin.
And here is the final product from two angles. This is one i'd like to strip and rebuild, there are several things I'd like to try to make better. Except for the diver, he's my favorite part.