FOA - Welcome to the best diorama forum on the internet. You have already gotten posts from some of the best around.
I like you ideas they are very nice, new and crisp.
I'll take it a picture at a time.
I like the rocky area with the shrubs around it, very nice and natural looking. The beach is well done too. I'd like to see a bit more sand piled up against a few of the rocks as a transition from beach to oasis (blown from the wind). IMHO I would like to see the trees taper a bit to the top. The back area is nice, fades away well.
The second one is really nice. I love the trees, good texture, fronds, color. The lower rocky area and sand are really nice (maybe a bit of blown sand).
The water is very nice, I like it a lot, the flowing part.
The rocks look a bit white for my tastes, maybe tone them down with some sand color pastels.
The red sea water is great. The reef is well done and the transition to the beach looks very well done. A few bubbles here and there but that the product not your work. They actually look good around the reef.
The trees don't quite make it for me. The shape is not quite right, they bulge to much in the middle. BTW - where'd they go in the last image?
So when I go to your red sea I'll just enjoy the sand.
Nice job.
Here are some of my water works for your critique

and

more here
https://armorama.kitmaker.net/photos/showgallery.php?cat=12054&ppuser=242I used the stuff in this feature
https://armorama.kitmaker.net//features/150Look forward to seeing you around.