
Visible crew/equipment: During Bud and Coffey's fight in the lab, we see a lightbulb swinging from side to side between the two men. If you look closely, you can see a hand (belonging to a third person) pushing the lightbulb. The only people in the room are Bud and Coffey. (01:44:16)
Answer: At the depth you're asking about, the water pressure is not enough to crush a diver's unprotected body (which is mostly solid/liquid and thus relatively hard to compress). The only thing they have to worry about is their lungs (gases, and therefore things containing gases, are much easier to compress). This worry is addressed by the pressure and composition of the air that they breathe on the rig, in their submersibles, and in their air tanks - this air has different proportions of gases (especially oxygen) compared to surface air, and is also at a significantly higher pressure - high enough to counter the pressure of the water that deep. (Side note: another way you can tell the atmosphere they are breathing in the rig is set at the same pressure as the water at that depth is that there is open water in the moon pool - and it's not rushing in to fill the entire rig, which it would if the air pressure was less than the water pressure).
Aerinah