This little gem is a rec-tekker's dream come true. It handles everything this side of helium-based breathing mixes and provides the diver several functions to adjust conservatism levels.
Packaging The Suunto D9 is an advanced diving instrument that looks the part. It's smaller than a standard computer yet has twice the beef of a typical watch, and its shiny accents over a brushed titanium body are eye-catching at a distance. The display uses larger, fatter numbers where readability is critical, making the D9 just as easy on the eyes as some of its larger counterparts.
Core functions The heart of the D9 is its RGBM algorithm and deep-stop capability (see sidebar). In fact, the deep-stop function is user-selectable and, when enabled, makes the first deco stop at half of maximum depth. On no-decompression dives, the D9 recommends a three-minute safety stop at 15 feet. Not making this stop incurs no penalty on future dives. However, if the diver exceeds the computer's ascent rate, a mandatory safety stop kicks in. Adhere to it and no penalties are incurred; blow it off and future dives will be shortened. If a deco stop is violated, the computer will lock up and allow no diving until the system has been cleared. The D9 handles three nitrox mixes, all of which can be programmed between 21 and 99 percent O2. The first mix reverts back to 21 percent two hours after a dive, but mixes two and three never default to another setting. It's also critical to know that the D9 will not allow the user to switch gas mixes if the switch would violate the set PO2 limit. Like other air-integrated computers, this one tracks remaining dive time based on air consumption as well as nitrogen loading and oxygen exposure. As an added precaution, the D9 bases calculations on surfacing with 500 to 725 psi in your tank, depending on whether the computer senses a fast or slow breathing rate for a particular dive. When it comes to dive planning, you can scroll through no-deco times for a future dive based on current calculations, but the computer will base those times only on the first breathing mix. (Of course, during the dive, calculations are based on the selected mix, not just the first mix.)
Bonus The digital underwater compass has been around for a few years, but Suunto has now made it part of a full-function dive computer. Numerically displayed bearings scroll up and down on a graphical compass rose. Bearings can be locked in and are noted in the memory for future reference. Visual aids help work predetermined search patterns. This compass is fully functional above and below water and can be user-calibrated.