Both my wife and I are certified scuba divers--although as residents of the Pacific northwest, we don't do as much diving as we'd like. We did just recently return from a trip to Bonaire, which was simply incredible, but that's a story for another day. Becoming a certified scuba diver isn't overly difficult, but you will spend a fair bit of time learning to read and interpret dive tables. When you first start diving, dive tables are a key tool in your portfolio--they tell you how long you can stay at a given depth, and more importantly, how long you can stay at a given depth on subsequent dives. (When you dive, your body retains nitrogen, which isn't a good thing. Over time on the surface, this nitrogen is naturally cleared--so the longer you stay on the surface after your first dive, the longer your second dive can be.)

While dive tables work well, they're a bit tricky to use, and subject to reading errors as you move down and across multiple columns, and flip the dive table from one side to the other. After learning to dive with tables, most scuba divers quickly move to dive computers, as they offer more power and much greater flexibility for divers, especially if you're making multiple dives per day. However, dive tables are useful as backups, as dive computers can and do occasionally fail.

So what's this have to do with the iPhone and iPod touch, you may wonder? Thanks to PunkStar Studios' Dive Planner, divers now have an electronic alternative to the dive tables.

Dive Planner is a very simple tool, with three vertical sliders dominating its interface: Pressure Group (which represents the amount of nitrogen in your bloodstream at the start of a dive), Depth, and Minutes Down. A fourth horizontal slider lets you set the planned surface interval between dives. Two large buttons toggle between readouts in feet or meters, and two boxes contain your pressure group after the dive, and after the indicated surface interval. And really, that's all there is. As you drag any of the sliders around, the pressure group readouts change to reflect the current settings. Compared to using a dive table, this is simplicity in action--a few quick finger drags, and you can see the pressure group for your current and planned dives.

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