A Penguin
Penguins were planned to be a semi-aquatic mob seen in the 2023 mob vote. They would have spawned on snowy shores and could have made your boat move faster. They also would have liked to jump out of the water and grab fish. Their appearance was planned to be based off of Crested Penguins.
The Penguin was the last mob revealed, alongside the crab and the Armadillo.