Most recreational divers learn to share gas using a conventional octopus. You breathe from your primary regulator, keep a brightly colored alternate secured somewhere on your BCD, and donate that alternate if your buddy needs gas. It's familiar, straightforward, and works well when everyone knows what they're doing.
But there's another approach. With primary donation, the regulator you're breathing from is the one you give away, while your backup sits just beneath your chin. When combined with a longer hose, the arrangement gives both divers considerably more freedom during a shared-gas ascent.
I use both configurations. When I'm working as a Divemaster with an instructor who prefers to teach using the conventional setup, that's what I use. Otherwise, I dive a long hose. I'm comfortable with either arrangement, but having spent time with both, I have a definite preference.
The Conventional Octopus
The conventional setup has one obvious advantage: you don't have to remove your own regulator to help someone else. You locate your alternate, release it from its holder, and present it to the diver who needs gas. Meanwhile, you continue breathing from the regulator already in your mouth.
It's an entirely reasonable arrangement, particularly for divers using rental equipment or diving with unfamiliar buddies. Most recreational divers have practiced it, and the equipment is uncomplicated.
What I like less is how the alternate is treated during an ordinary dive. Ideally, it's secured somewhere accessible, checked before entering the water, and ready when needed. In practice, I've seen plenty of octopuses dangling beneath divers, tucked into inconvenient places, or dragging along the bottom.
Even when everything is where it belongs, you're donating a regulator that hasn't been in use during the dive. That doesn't mean it won't work, but it does mean you're relying on something you haven't been breathing from.
There is also the possibility that a frightened diver won't look for your octopus at all. They may simply reach for the regulator in your mouth, which is exactly where your training with a conventional setup may not have prepared you to donate it.
Why I Prefer a Long Hose
With primary donation, you give away the regulator you've been breathing from and switch to a backup secured beneath your chin on a bungee necklace. It's a different way of arranging the same two second stages, but the consequences are significant.
First, you know the donated regulator was delivering gas moments earlier. That isn't a guarantee against a malfunction, but I find it reassuring compared with donating an alternate that hasn't been used since the pre-dive check.
Second, the arrangement anticipates someone taking the regulator from your mouth. If a distressed diver grabs your primary, that's already the regulator you intended to donate. Your backup is waiting in a predictable location, rather than being secured somewhere on the front of your BCD.
Then there's the hose itself.
Sharing gas on a short octopus hose can be surprisingly awkward. Two divers have to stay close together, and every change in position risks pulling on someone's regulator. Give them several feet of hose and suddenly they have room to maneuver, control their own buoyancy, and ascend without practically embracing one another.
That extra room is valuable during perfectly ordinary recreational diving. You don't need to be exploring a cave or squeezing through a wreck to appreciate it.
Of course, a long hose must be routed and retained properly. If it's trapped beneath your equipment when someone needs it, its length becomes a liability rather than an advantage. The regulator must be easy to donate, the hose must deploy cleanly, and your backup must be immediately accessible.
Those are things to practice in the water, not merely assume will work because the equipment looks right.
The Backup Regulator Suddenly Matters
There's something rather funny about switching to primary donation. When you realize that you're the person who will be breathing from the backup regulator during an emergency, your attitude toward that regulator changes.
In a conventional setup, the octopus is often treated as something reserved for someone else's problem. You may never breathe from it underwater except during a training exercise, and it's easy to regard it as secondary equipment.
With primary donation, that backup becomes your own breathing supply when your buddy needs gas. Suddenly you pay closer attention to its performance, maintenance, and accessibility. You're considerably less inclined to buy the cheapest second stage available simply because someone labeled it a backup.
Both regulators should be dependable regardless of configuration. But I find that primary donation has a useful way of reminding you why.
Being the Odd Diver on the Boat
Most of the time, I'm the only person on a recreational dive boat using a long hose. That means my assigned buddy is probably accustomed to a conventional octopus and may never have seen my configuration before.
I'm not going to assume they understand it.
Before we get in the water, I spend at least a minute explaining what they're looking at. I show them that I'll donate the regulator in my mouth, where my backup is located, and how the long hose deploys. If they've never seen the arrangement, a demonstration is far more useful than simply telling them I'm using primary donation.
It's part of the same practical approach I take to Insta-Buddy Checks. When you're diving with someone you've just met, a short conversation about how your equipment works can prevent a great deal of confusion later.
And it goes both ways. If my buddy uses a conventional octopus, I want to know where it is, how it's secured, and what they expect me to do if I need gas.
The equipment configuration matters, but the two divers understanding each other's equipment matters considerably more.
Which Should You Use?
I prefer the long hose because I like donating a regulator I was just breathing from, having my own backup immediately beneath my chin, and giving both divers more room during the ascent.
But I don't believe every recreational diver needs to switch. A well-maintained conventional octopus, correctly positioned and used by someone who has practiced with it, is a perfectly reasonable solution.
What I would discourage is choosing either configuration without understanding its weaknesses. A conventional octopus isn't particularly useful if nobody can find it, and a long hose offers little benefit if it cannot be deployed properly.
Whatever you choose, practice sharing gas while hovering, swimming, and ascending together. Those situations reveal problems that a regulator exchange performed while kneeling on the bottom rarely exposes.
I've covered the actual emergency, including how both divers should respond when things don't go according to plan, in Sharing Gas: What Both Divers Need to Do.
For my own diving, the long hose remains the better arrangement. When I'm working with an instructor who teaches conventional donation, I'm equally comfortable using that system. Understanding both has made me a better buddy, regardless of which regulator happens to be in my mouth.