During ascent, your body needs time to adjust to changing pressure, and you need time to regulate your buoyancy, keep track of your buddy and watch for obstructions overhead. It's important to ascend slowly - no faster than 18 metres/60 feet per minute, which is slower than you may realize.

As a new diver, you may find it a little difficult to judge your ascent rate at first. No worries. Star your ascent with plenty of air so you can make a slow, leisurely trip to the surface. Preferably, ascend along a line or follow the bottom contours to give you a visual reference and help you gauge your speed. Use your depth gauge as you ascend to help you know how fast you're going up, particularly when ascending without a visual reference. It should take you at least 10 seconds to ascend 3 metres/10 feet - but don't worry about being exact, as long as you're not exceeding this rate. In fact, it's a good idea to come up slower - most computers and gauges warn you if you exceed 10 metres/30 feet per minute.

Whenever possible, stop your ascent when you reach 5 metres/15 feet and wait three minutes - more is fine - before continuing your ascent, particularly after deep dives or dives close to the no stop time limit. This is called a safety stop (you'll learn more about safety stops in Section Five), which gives you an extra margin of safety.

Think of the 18 metre/60 foot per minute rate of ascent as a speed limit. It's fine to go slower, but don't go faster. Be a S.A.F.E. diver: Slowly Ascend From Every dive.

Dive tables and dive computers use mathematical models to estimate the theoretical nitrogen in your body before. during and after a dive. People vary in their susceptibility to DCS, so no computer or table can guarantee you'll never get DCS, even Within its limits. So, dive well within table/computer limits. Dive computer has some use advantages and disadvantages compared to tables, but it is neither more nor less valid. Recreational divers only make no decompression (no stop) dives.