Think I Bottomed Out at 300' on OC

[amascuba]

If it has a CO2 scrubber and you're reusing the gas (breathing it more than once) to extract more O2, I think it's classified as a rebreather.

Bingo. The only difference in a CCR and a SCR is how they add gas back into the loop. SCR adds a pre-mixed gas back into the loop and a CCR adds gas into the loop based on a set point to keep a constant PPO2. They both, however, recycle exhaled gas through a chemical scrubber.