Rebreather

Hollis Explorer

Hollis

A semi-closed rebreather (SCR) from Hollis, aimed at recreational divers rather than technical ones. Semi-closed units vent some gas on every breath rather than recycling all of it, which makes them simpler than a full closed-circuit unit but more limited. Now discontinued, though units remain in use.

1 instructor in the directory across 1 dive centre dive or teach the Hollis Explorer. The qualifications listed under each name are the closed-circuit courses they hold — which is what determines the depth and gas mixes they can teach.

New to rebreathers? One thing worth knowing

Rebreather training is tied to the exact machine you learn on, and courses go up in steps — you start shallow and add depth and gas mixes as you progress.

If you later switch machines, you keep what you’ve earned. You do a shorter changeover course on the new one and carry on from where you were. That works the same way whichever agency you trained with, so it isn’t something you need to plan around.

Instructors are the exception — and it can affect how far they can take you on this machine:

  • An IANTD instructor who moves to a new machine keeps teaching at the level they already taught, once they’ve built up enough hours on it.
  • A TDI, SSI, PADI, RAID or GUE instructor who moves to a new machine starts again at the beginner course on it, and works back up as they certify students.

What that means as you read the list below: someone may teach to a greater depth on their main machine than they currently can on the Hollis Explorer. Where that’s possible we’ve flagged it — if you have a target depth in mind, just ask them what they teach on this one.

It cuts the other way too. Because a TDI, SSI, PADI, RAID or GUE instructor has to work back up on each machine, they will usually have more hands-on experience actually teaching students on this particular machine. That is a different thing from experience on the machine — an IANTD instructor may have far more personal time diving it, and may well have taught plenty on it too. Worth asking either way.

rebreather depth & gasoverhead — cave, wreck, minealso trains instructors

Instructors Diving This Unit

Dive Centres Supporting This Unit

We're still building out the directory country by country, so this list isn't every Hollis Explorer instructor or dive centre in the world — more locations are coming soon.

Last updated September 7, 2026