I dive a Prism2, but am using it for technical & cave diving. That said, my instructor teaches both the Prism2 & the Explorer & the Poseidon MK VI . As mentioned above, it is strictly a recreational hybrid (mostly a semi closed) rebreather. It is good for 2 hr dives with the sorbant & under the MOD of the "drive gas" used. It is affordable to many, more so than a fully closed rebreather. The unit is very useful for longer dives without the weight of doubles (back or side mounted), It only periodically releases bubbles, so doesn’t scare the marine life as bad as open circuit. Many photographers like this option. My favorite part of the Prism2 is the quiet. Other than the solenoid injecting gas & the movement of the counterlungs, it is completely quiet.Something to keep in mind with rebreathers, whether semi or fully closed is there is considerable maintenance that MUST be done, both pre- dive & post dive, there are no short cuts. Check lists must be followed to the end. Period. My prism requires 2- 3 hrs of pre- dive work & about 2 hours of post dive work. Not trying to persuade or dissuade you either way, just putting out the positives & minuses.