Many people buy a new computer and use their old one as a back-up, only to find that it works on a different algorithm and so gives conflicting information.
You are then left with the choice of managing your dive by the most conservative algorithm or bending a computer and rendering it useless for the next 24 hours.
The important thing is to match your back-up to your first choice, which in many cases can be expensive. So the Oceanic BUD is intended as a cheaper way of backing up another Oceanic computer.
This said, I broke all my own rules by taking it diving alongside a couple of Suuntos.
The BUD comes in a standard hockey-puck-style module that clips onto a BC or a camera.
I chose to use the latter. It is extremely lightweight, but doesn’t float annoyingly when it’s under water.

The BUD is a single-gas, variable-mix nitrox computer. In common with all modern
Oceanic computers, it gives the user a choice of algorithm.
You can set it to work to the traditional Oceanic Pelagic DSAT program or choose the Oceanic Pelagic Z+ algorithm. This is based on a typical Buhlmann ZHl-16C model currently employed by many of the smaller European dive-computer manufacturers.
What’s the difference Well, the Pelagic DSAT program is intended for use by those divers who like to dive several times a day, but only for short periods and not very deep.
It’s intended for no-stop diving shallower than 30m. If you go deeper, or into mandated decompression stops, it uses a very different set of figures, and deco times can become punitive.
Stay within the parameters intended, and it will give hours of no-stop time. So you can either
use it and do dives that probably don’t even need a computer, or tie it on a line under the boat to do the stops while you’re having lunch after the dive.
The Oceanic Pelagic Z+ program is much like the model you’d expect from any European computer. The important thing is to set the one that matches your main computer.

Apart from the algorithm, you can choose an additional conservative or safety factor, and of course you must set the oxygen percentage for the air or nitrox being used. This is all done using a single button with long and short pushes to navigate in sequence through the menu.
In common with nearly every other computer, the BUD samples the air pressure and sets the altitude automatically, and turns on without prompting when immersed.

In the Water
For my first dive with the BUD, I was feeling mischievous enough to use it with the Pelagic DSAT algorithm. It was totally out of step with the Suuntos alongside it, and suggested I had more than two hours of no-stop diving left when the Suuntos were running out.
I left it for a couple of days, and then took it set with the Pelagic Z+ algorithm and a safety factor added on a long 30m-plus dive, during the ascent from which I was intending to be caused to make a decompression stop.
In this case it was more conservative than the Suuntos in their standard settings, even though they had done some repeat dives during the intervening period.
I was bemused to see that as the BUD began to run out of no-stop time, it displayed the word UP in a very definite way. Then it clocked up about 12 minutes of stops at 3m, compared to the matching pair of Suuntos’ four.
That’s the problem with using the BUD to back up a computer of a different make. In reality, it works only with any modern Oceanic computer, and provided you match all the settings – or, of course, you could choose to use it as your only computer.
In common with many other US dive-computers (Oceanic’s computer subsidiary also makes them for other brands) the BUD displays a bar graph round one side of the dial that indicates progression towards deco-stop diving, and another on the other side of the screen that indicates ascent rate.
You get your most important information as a primary display, and pushing the button under water gives you secondary information such as nitrox mix and actual pO2 at the depth you’re at.

If you’ve splashed out on an expensive Oceanic OC-1 computer and feel you need something to back it up, the BUD is an ideal solution.
However, if you are backing up a computer of a different make, I suggest you get yourself the entry-level computer of the same brand.
Oceanic claims that you can match almost any other computer by selecting the algorithm and appropriate conservative factor.
I’d take issue with that. You can get near, but not near enough. The BUD is not so cheap that some other computers cannot compete on price.

Mares Puck, £190
Oceanic Veo 2.0, £255
Suunto Zoop, £199
TUSA IQ650, £203

PRICE £179
ALGORITHM Dual (Pelagic DSAT or Pelagic Z+)
DISPLAY Depth, duration, no-stop time or deco
ALTERNATIVE DISPLAY Nitrox mix, actual pO2, oxygen exposure
GAS Single-mix air and nitrox to 50% O2
BATTERY User-changeable
CONTACT DIVER GUIDE width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100%