[Jack Hammer]

RIP, Troop.

Just parenthetically, I was under the impression that rebreathers could NOT be used below forty feet.

Anyone know for sure?

[driftdiver]

Depends on the type of rebreather from what I understand. Some are limited to very shallow depths.

The advanced ones avaialble on the open market are routinely used for dives to 200 to 400 ft. There are dives down to a 1000 ft using rebreathers.

[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.