Recently I had the opportunity to complete the Hollis Prism 2 Rebreather course. My previous experience on the Poseidon Mk6 meant that I was able to focus more on the Prism2 than the actual difference between open and closed circuit diving.
Immediately I noticed the shape and position on the front-mounted counter lungs I was using. The shape leaves you much more room for head movements but as it widens lower on your chest it still provides heaps of volume and has integrated weight pockets which paired with non-ditchable pockets on the tank bands made for ample weight for saltwater diving in a dry suit.
In all positions, I found the work of breathing easy from a normal prone position to upside down and on my back the changes to my ability to breathe were negligible
The way the gauges come through the counter lung is also really convenient. It is easy to find them and tilt towards your eye and they’re extremely streamlined.
I found the computer really easy to understand and read even with little experience with shearwater computers, Changing setpoints, using the compass, bailing out, navigating the menu with only two buttons was actually really seamless. Likewise with the heads up display, with one button and twelve LEDs you at first I thought I wouldn’t make sense out of it. But again seamless. When manually keeping your setpoint it is really easy to use just the heads up or computer while swimming and performing skills.
The radial scrubber is really simple to pack. With a golfball to covering the center, you hardly make a mess. A few taps and turns and while filling gets a good solid consistent pack down and you’re away. With the clear canister bucket, you can be sure your scrubber is in place and dry.
Using 9v and AA batteries for the solenoid and HUD and computer makes it so easy and cost-effective to have spares with you and they all work separately. If your HUD goes down during the dive your computer works if your batteries run out for your solenoid you can manually add o2. But of course, the computer gives you plenty of low battery warning.
The BOV is quite nice in the mouth although I found I needed two hands to switch from OC to CC. Even having to be quite forceful I never felt like I was going to lose it out of my mouth though.
Basically, I really enjoyed diving in this unit. I spent just over 8 hours diving it and won’t hesitate to use it again and even have plans on buying my own eventually.