This website has really cool themes to carry throughout your classroom. I found the ocean one to be interesting because one the swimming pool in the picture. I feel like you could use this as a reward for students that had outstanding behavior where they could do either their reading or writing in the swimming pool.
Aquarium in my toddlers classroom. They made the fishes, octopus, whale, turtle and starfishes. All the windows are cover with blue cellophane that creates the perfect aquarium atmosphere for kids to learn about the sea animals.