[Travis McGee]

Unlike nitrogen bubbles in the joints, oxygen pressure tolerance varies widely between folks. Before BUD/S, potential trainees have to sit in a re-compression chamber breathing pure O2 for an hour or so, while corpsmen watch them closely. I forget what the simulated depth on the test was, it might have been 60’ of pressure for 60 minutes, but that is just a guess based on a 30+ year old memory.

In general, frogmen level out and swim at about 30’ to the target. If a ship was coming overhead in a harbor, you might dive down to 60’ until the ship passed by. But in general, 20-30 feet was the cruising depth on oxygen.

[driftdiver]

Oxygen becomes toxic at certain pressures. On 100% oxygen your safe depth is only about 40 ft to avoid oxygen toxicity. As you said it depends on the person.