Nobody enjoys working the dive tables, but they're an invaluable tool for safe diving. Dive computers are an even better tool for the same reason a laptop is better than a slide rule.

By constantly monitoring depth and bottom time, dive computers automatically recalculate your no-decompression status, giving you longer dive times while still keeping you within a safe envelope of no-decompression time. Computers can also monitor your ascent rate and tank pressure, tell you when it's safe to fly, log your dives and much more. That's why dive computers are almost as common as depth gauges these days.

What to Look For:User-friendliness. The most feature-packed dive computer does you no good if you can't easily and quickly access the basic information you need during a dive: depth, time, decompression status and tank pressure. Some models have both numeric and graphic displays for at-a-glance information.

Mounting options are an important feature to consider and let you position computers on your wrist, gauge console, hoses or attach them to BCs.

Some computers are conservative in their calculations, automatically building in safety margins; others take you to the edge of decompression and trust you to build in your own safety margins.

Before you buy, ask to see the owner's manual and check it out. Complete and easy-to-understand instructions are important, especially on feature-packed machines.

Cost: $250 to $1,300.

Begin with an honest evaluation of your diving needs­do you plan to use mixed gases someday to do decompression diving? Study the features of different computers and choose the one that offers the mix of features you need at the best price.