What little girl doesn't love Little Mermaid? I know mine certainly does! I actually made this bath upon her request.
The craft foam seaweed is perfect to use for counting practice! They can be taken off and put back on, counting each time. When wet craft foam magically sticks to the walls of the bath tub which makes them fun to play with and also great for decorating and making the theme come to life more. We cut ours out from some green craft foam purchased at Micheal's.
Coral Reef bath paint was another fun addition to our Little Mermaid Themed Bath. To make it I squirted some shaving cream into a clear plastic bowl that had flip-flops on it. (I thought that looked beachy and kind of fit in with the theme). Then I added in a few drops of red food coloring, and a few drops of yellow food coloring and mixed the two together with a makeup brush until I got the coral color I was trying to make.
I laid out some sponges that came with my daughter's Little Mermaid paint set so she could use them to make some themed prints on the bath tub walls! Those really made it special. I'm sure you could find paint sponges shaped like different things at craft stores and maybe even Dollar Tree.
I also had a bowl of seashells sitting there for sensory exploration and themed play.
Afterwards my daughter got in her mermaid bath towel :)