Under The Sea

The other day, I wanted the ocean, so I started this piece:

I started by mixing a couple of blues and painting the canvas. My first thought was to use some of the massive collection of shells I have. After adding them to the corner, I was looking through some inspiration on my computer and decided I needed a mermaid. The one I chose is from The Sum Of All Crafts blog. After that I decided I needed some seahorses around her. I went to Micheal's, The Dollar Tree, and Making Memories on Wednesday, but couldn't find the right ones. I went to Hobby Lobby yesterday and found the blue ones, and decided the yellow one I had to begin with (also from The Sum of All Crafts) would work well. The blue ones are layered paper with googly eyes.
Now, I'm stuck, I know it needs more, but I'm not sure what. I think it needs more dimension and probably some plants, but I don't know where to start.

Any ideas?