This looks better than many of the other underwater terrains lately. You actually used fish and such and the general doodad use and placement is fine.
Things to improve...
Tile variation could be improved, it is okay but still could be improved. Also the ship is too small compared to everything else.
Do people like you that always brabble about the tilevariation think the terrain of 'Desert of Exile' is great? Because rly the tile variation of that map is 'way-over-the-top'