How do allow the player to see the surfaces of a part while being inside the part?

The title doesn't really explain it, but I want to make an ocean out of a part or multiple. The player can swim in the water, but when the player puts their camera in the water, they can see the ocean floor. I don't have anything in the water, but when the player puts their camera in the water, they can see right through the surface of the water.

Above the water: The player can see the surface

Below the water: The player can't see the surface

If there's a script, property, or type of material that can solve this, then please tell me. :D

Thanks.