My little girl is 14 months old and loves a little battery operated swimming toy we have for her bath. I was looking for something similar and came across these wind up toys. Overall they work good and are entertaining, but I wish they would move a little more.
This 3-pack of wind up bath toys comes with a frog, whale, and tugboat. The frog and whale both have little knobs on the bottom, and the tugboat has a larger knob on top that winds them up. The frog is my favorite because it swims by kicking its legs. I think of all three, the frog moves the best too. The whale swims by flipping its tail up and down, but it doesn't move very much. For some reason the boat only "swims" in circles, but my little girl loves to twist the wind-up knob. They all last for about 30 seconds with a full wind up.
One thing I will note about these is that they are louder than I thought they would be. At first, my little girl was not sure she really wanted to touch them because they were making an odd new noise. Now that she is used to them, she hands them to us constantly so we can wind them up. She likes to hold them while they unwind more than she likes to watch them swim around.