That coral looks pretty nice, yes it is beautiful , but a little too BIG.
Perhaps a smaller sized coral reef might
be more realistic (?) I have at home a folder with about 500+ photos, of many coral
reefs for my artsy stuff. Maybe you would like to use some?
There is also google earth and you can fly over north Australia where they have many
reef corals and take photos of that surrounding area.
To add sharks to this image would be unreal also. They would look like giant prehistoric
sharks or 3 times the size of a normal large-sized great white shark, because of
the size of game skins.. but there is a nice fish that you can add, and that is a Whale-shark.
It looks very beautiful looking
at it from the top. Has many tiger-like lines and spots on it.
They are about the size of a medium sized whale, but are often found on open sea.
Also Black Mantas are pretty huge sea creatures and might look good
on swimming around the coral reefs , which in real life, they actually do. Some grow as
big as about the size of a cessna airplane.
This might help
Google image search - " flying over coral reef " many nice photos showed up on this search
see this film, SKIP to 01.57 minutes =