Hollis Prism 2 rebreather media event

Hollis Prism 2 rebreather test team

Hollis is a household name in the UK recreational and technical diving world, and now has plans to make inroads into the growing rebreather market with the Prism 2.

Prism 2 is a unit developed over a long period with the clout of a global manufacturer behind it

The Prism 2 fully closed circuit rebreather (CCR) is the ultimate refinement of a unit that was launched back in the early 1990s at the dawn of bubble-free sport diving. If you choose to become a Prism 2 diver today, you are buying into a unit developed over a long period that has the clout of a global manufacturer behind it.

I was fortunate to be invited to the National Diving and Activity Centre in Chepstow for an introductory session with the Prism 2 – although regrettably I was unable to try-dive because of Covid restrictions. Nevertheless, the day was a useful insight into the unit and the people behind it.

Trevor Leyland presents the Hollis Prism 2 rebreather

At this point in the story we introduce Trevor Leyland, who is owner of south coast outfit TAL Scuba, a technical and military diving instructor, and longstanding rebreather specialist. He also in his own words ‘fell in love with the Prism’ almost a decade ago. Today he runs Rebreathers UK as the main distributor dedicated to sales and support in the UK, and since 2019 has extended this reach across much of Europe too. For the media event Trevor had enlisted an impressive team of support divers from across the UK, to assist attendees on the day but also to display the network of instructors and service centres already in place for Prism 2 owners.

Checking out the NERD display for the Hollis Prism 2 rebreather

A short history of the Prism 2

Hollis may be US-based but this rebreather actually has its origins in a British-designed unit, created by a chap called Peter Readey in the 1990s. His ‘Incredible Steam Machine’ joined Peter’s initials to become the P.R.I.S.M. and gained enough of a following to catch the eye of Hollis in 2007, who embarked on an update and redesign programme and prepared the P2 for large scale manufacturing and quality control. In 2012 the Prism 2 was launched in the USA with a series of updates and sister company Hollis Rebreathers LLC was set up to focus on this element of the business. Worldwide sales began in 2017, with CE certification for EU sales granted as recently as late 2019.

Ladies love the Hollis Prism 2 rebreather

Benefits of this rebreather

The Prism 2 is a fully closed circuit rebreather (CCR) which promises users the standard benefits of diving this way – namely longer dive times, extended range and deeper dives, warmer breathing gas with less fatigue, and even silent diving for ambushing wildlife (useful for photographers.) Trevor also believes the P2 is safer than open circuit due to the numerous bailout options it provides, and this unit is ideal for travelling as it weighs less than 20kg. He also highlighted the ‘cool’ visual factor, best described as a black/white/red behemoth that gives it the look of a stormtrooper’s backpack.

Zoe of DIVER magazine and Pete of Deep Blue Pirates with Hollis Prism 2 rebreather

There’s a pleasing symmetry and simplicity to how the Prism 2 is presented, and it turns out this is reflected in the design beneath. Trevor enthuses about how easy the Prism 2 is to clean, with a reliability delivered by design: there are few failure points, it’s easy to fix and the bucket is made of a clear urethane bucket so he can see the radial scrubber, should it ever flood. Good design is not just about a machine’s performance, and the Prism 2 is inherently a good design: for example, it uses standard batteries rather than obscure ones, if you need to replace them in a far-flung location. The latches that secure the bucket to the head are held in place by the cylinders either side, so they won’t come undone even by accident. The bucket is clear so the user can see the radial flow scrubber inside. Left and right components including valves are colour-coded and thread differently, to prevent incorrect assembly: and so the list of good design elements goes on. Unlike some units the Prism 2 does not have inaccessible failure points that could catch the user unawares.

Performance and features

Under CE test conditions, the Prism 2 gives just over 3.5 hours when used with Trimix at 100 metres, in 4-degree C salt water. The radial scrubber holds 2.7kg of sofnolime, which delivers a low resistive effort through the dive supply valve (DSV) or optional bailout valve (BOV) – which has a built-in backup second stage. Buyers can choose from front-mounted counter-lungs (FMCL) or back-mounted counter-lungs (BMCL), and their choice of either a Hollis harness and wing or third-party option. The electronics are based on tried and trusted Shearwater, with a head-up display (HUD) flashing coloured LEDs in the diver’s eyeline. It’s a familiar setup to many, offering full mixed gas decompression management through the wrist-mounted computer and controller. The brilliantly bright screen can also be connected to a NERD display which looks like an eyeglass mounted above the loop with a full colour display inside.

Four Hollis Prism 2 divers ready to go

Put together, this design and its components gives the Prism 2 some impressive performance characteristics. It has a better partial pressure of oxygen (PO2) in the loop and allows it to be monitored more accurately. Trevor says this gives the unit more stability, makes it more predictable and reduces the less risk of hypoxic (too little oxygen) and/or hyperoxic (too much oxygen) loop conditions. This also enables the user to respond more quickly to changes in diving conditions and depth changes, with lower O2 waste and a more stable loop volume.

Mark Evans of Scuba Diver Magazine using the Hollis Prism 2 rebreather

Factory support

The Prism 2 brings something different to the rebreather party, which is full service support from a specified dealer network spread around the country. Users of other units have been left frustrated by the requirement to send their rebreather abroad for a service or repair, often at considerable cost and for frustratingly long periods. Even factory servicing in the UK can be measured in months, rather than days or weeks. Because Rebreathers UK is based on the south coast, it can offer authorised factory servicing for Hollis without the need to ship overseas, and the dealer network (which is growing all the time) can offer support, as well as instructor training and ongoing guidance.

Hollis Prism 2 rebreather

In the water

Representatives from the media paired up with Scott (Sandford and Down), John (Dive Manchester) and Peter (Deep Blue Pirates) and ran through the checklist to prepare their units. It was then all aboard the familiar minibus for the ride down the long ramp to the water at Chepstow for an hour test diving the Prism 2 in the shallows. Trevor had assembled a number of other Prism 2 divers to act as in-water support and bemused onlookers suddenly found themselves outnumbered on a Saturday afternoon by this army of rebreather users.

Mark Evans of Scuba Diver Magazine using the Hollis Prism 2 rebreather

Post-dive and the mood from the magazine reviewers was enthusiastic, so it will be interesting to see the write ups when they appear in DIVER, SCUBA and Scuba Diver magazines. It has been a long road for the Prism 2, but it seems all the elements are finally in place for many more people to own and use this impressive machine. Hopefully in due course, I’ll be one of them.

Thanks to Hollis Rebreathers UK and Trevor at Rebreathers UK for the invitation.

Hollis Prism 2 rebreather