Surface intervals are usually taken up with recharging batteries, downloading memory cards and writing notes on my laptop. I also like to take a shower if I can, and enjoy a meal.
So you can see that an interval doesn't allow me much time to sit around or play about unnecessarily with kit.
Contrary to popular belief, I am not an equipment freak. Naturally, I always use a full set of equipment when I dive, and I find it no hardship to try new kit and note down my impressions for the DIVER Tests pages. It's a task that dovetails easily with what I already do.
But I have neither the time nor the patience to bother with kit that takes too much effort to understand. I don't expect to have to read the manual unless I'm really stuck, and even then I often ask for a second opinion.
This is why I appreciated the simplicity of the Mares Puck Air computer. It's like the good-value Mares Puck, but it is integrated with your breathing gas via a permanent connection to a high-pressure hose. It's a full-function decompression computer that uses a variation of the Wienke RGBM algorithm.
Mares says: The Mares-Wienke RGBM (Reduced Gradient Bubbles Model) algorithm takes into account the phenomenon of micro-bubbles in order to prevent their formation to the greatest possible extent.
In more than 10,000 real dives monitored by Dr Bruce Wienke in the Los Alamos laboratories, the formation of micro-bubbles has been studied and evaluated in order to better understand the mechanism behind how micro-bubbles are formed during a dive.
Today it is the most evolved algorithm for reducing the formation of micro-bubbles without compromising dive times.
One version comes with an analogue compass mounted on it's console.

The Puck Air has a single button, a quick push of which accesses the full range of menu layers. Hold the button for a second or so and you enter that layer. Quick pushes manoeuvre you through the layer of sub-menus, and a long hold accesses it. Quick pushes make adjustments and long holds confirm the setting.
The only disadvantage seems to be that if you overshoot a setting, you have to scroll right round to get to where you came in.
Mode, data, alarms, time, watch-display settings such as contrast, PC link, logbook, planning and even access to the computers serial number are accessed this way.
You can leave the unit set for air, for nitrox or simply use it as a bottom-timer and depth-gauge. There are three variations of a personal adjustment to make the program more cautious.

Display Legibility
See the legibility for yourself in the picture. The display doesnt bombard you with unwanted information. It tells you your depth and remaining no-stop time and tank pressure.
Because it has a dot-matrix display insert, warnings come up with real words rather than symbols or icons, the meaning of which might be obscure (Ive never worked out the significance of an icon that looks like an ambulance!).
One grouse is that as soon as you stop being attentive towards the display at the surface, it switches off. It has a powerful backlight.

In the Water
My only other grumble was that the hose was a little on the short side. This meant that, although I could tuck it away neatly so that I didnt club benthic animals to death with it as I passed, it was hard for me to hold it up to photograph.
I managed, however.
Besides actual tank pressure, the Puck Air gives you a prognosis of how long your supply will last, based on your actual depth and your breathing rate up to that point.
Of course, a variable reserve of 50 to 120 bar is built into this calculation if you so choose to set it. It automatically displays a safety stop of three minutes once you get shallower than 5m.
The algorithm delivered no surprises, and it dovetailed well with other European computers I had with me on the dives.
The Puck Air is a very straightforward computer for straightforward leisure diving.

Planning and Logbook
Planning mode simply scrolls through a range of depths and no-stop times adjusted to suit the nitrox mix set. Logbook shows maximum depth, dive duration, initial and remaining tank pressure and water temperature. It also records whether you exceeded maximum ascent rate.

Mares Nemo Air, £349
Suunto Cobra, £520

PRICE £350
IN-WATER DISPLAY Depth, remaining no-stop time, dive time, ascent-rate, oxygen exposure, tank pressure, remaining air-time.
DECO INFO Ascent time and stop depth.
MODES Nitrox, Air, Gauge.
BATTERY CR2450 user-replaceable.
DIVER GUIDE width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100%