In case you didn't notice, I posted some more coral reef items.

Another idea, when I made my waterfront map, the main focus was the water and the ships with the underwater items just barely visible. I used a solid water base and placed the submerged items on top of the water but with a low opacity ( about 20% ). So even though they are above the water, they look like they are under it. Not sure if that will work for you, but you could try a little higher opacity so the submerged art shows more. https://www.deviantart.com/bogie-dj/...sion-759496091

Also here are some transparent water fills I have:
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