The Manta Storm
From the Super Mario Wiki
When the player first enters the level, they will find that Hotel Delfino has vanished under a pile of electric goop. Talking to the hotel manager near where the hotel should be will have him explain the situation to Mario. According to him, a large manta-like being came from the sea and covered the hotel in goop (which is shaped like the manta itself), causing it to sink. In the middle of the conversation, the Manta itself will slide onto the beach and the battle will begin.
The Manta leaves a trail of electric goop behind it when it moves. Spraying the Manta with F.L.U.D.D. or attacking it with Water Barrels will cause it to divide. Each manta will divide into two more when sprayed long enough. The mantas will move in random directions, all leaving a trail of electric goop behind them. To defeat the Manta, the player has to continuously spray it until it can no longer divide. Once all that remains are the smallest possible mantas, they will get angry and begin trying to attack Mario. If Mario comes into contact with one, he will take damage and be thrown off. When the player finishes spraying all of the mantas, the hotel will return, the beach will be cleaned, and the Shine Sprite will appear.
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