How do I stop him from going out of the water?

Development Character & Animation
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1

He has a projectile movement and is homing to my player.

2

Hey there @VKittyCat2022! You will have to clamp the vertical location of the fish to the water. I think you can use GetWaveInfoAtPosition and use the InPosition output as the clamp value.

3

Maybe you just need to add a collision box slightly above the water surface to block it.