How do i fix this bug with my 3d model?

i am working on my third person 3d game. the problem is sometimes i can see the water (it is a transparent cube) trough the player. some parts of the player are sometimes visible trough the shell part too

the legs are meant to be in the cube i mean the torso

whatever you made your model in, try recalcuating the normals

well i made it in blender. i tried to recalculate normals but nothing changed.

did you try recalculating the ground instead?

if you mean the water i cant do that as i use the gdevelop cube

is the size of the cube negative?