If you’re building a robot then the humanoid shape is a fairly good shape to use because the world is already designed for things of that shape. Doors, corridors, and staircases all assume a bipedal body of about 6 ft high. So inevitably robots are going to look humanoid.

If the robot is designed to work underwater then it probably isn’t going to look humanoid it’ll probably look like a fish but I don’t think the fish can sue.