The monster in episode 21 was created by Michiru. She used a piece of meteorite that belonged to Mai's father, and turned it into a star shaped monster. This was the only monster that Michiru and Kaoru created.

The monsters in episodes 25 to 32 were created by Mizu Shitataare.

In episode 25, the water of the ocean was turned into an ice monster. In episode 26, a water faucet was turned into a monster.

In episode 27, some water balloon yoyos were turned into a monster. In episode 28, some ice crystals hanging from the inside of a cave were turned into a monster.

In episode 29, some soap bubbles and the soap bottle were turned into a monster. In episode 31, a water fountain was turned into a monster.

In episode 32, the water in the school grounds was turned into a snake-like monster.