I love the fish cubes...however, I don't think the beige block works. It is to plain compared to the rest of your blocks.
Maybe if you could find some dyed fabric with different blues for the inside of the block so it looks more like water. Have you sewn these blocks together yet? If not you could space some plain blues between the fish blocks. If you could find ANY fish fabric you could cut and applique fish on some of the dyed fabric and still leave some plain.