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.
Wow - didn’t know that. Thanks!
Mixed-gas rebreathers can be used very deep. Pure oxygen rebreathers are for shallow combat dives. Instead of going down 400’ and working in one area for hours on mixed gas, combat swimmers may swim for 3 hours toward a target at 25’ depth, leaving no bubbles at all. Nary a one. All using that little oxygen bottle at the bottom of the Draeger rig.