The issue of ascent rates must be looked at from many angles. Dr. Bennett provided a very useful and well put scientific angle in Haldane Revisited that all divers should be made privy too - particularly dive leaders and those that write educational standards and procedures. I would like to address the diver skill angle of safety stops and ascent rates. The safety stop, as Dr. Bennett well explained is important for dropping "fast-tissue" tensions. It also is important for decreasing the risk of making rapid ascents in the last part of the ascent.

Can you relate to the following experience at any point in your dive career: one minute your gauge reads somewhere between 15-10 feet and then seconds later you are staring at the surface less than 2 feet away. "Wow, how did that happen?"

We tell divers that they should make safety stops and perform 30 ft/min (9 m/min) ascent rates but are we teaching them how and making sure that they can achieve them? We watch thousands of diver ascending annually with diver certifications ranging from entry level to course director and I can tell you that the answer to that question is a resounding "no." The medical community is doing their part, but without diving educators and leaders to make sure research findings are put in practice then we all fail.

Let us look just at the term 30 feet per minute. What does that mean? Can you walk at a rate of 30 feet per minute accurately? How about a rate of 45 feet/min or 70 feet per minute? How can you measure that while doing it? Can you tell when you are driving 45, 60, 60 mph without looking at your speedometer? It is fine for scientists to say 30 feet per minute, but it is not fine for dive instructors and leaders. We need to give divers a Usable term such as two seconds per foot. Ahhh, now they can ascend by counting two seconds for every foot their hands move upwards on the anchor line, or they can look at their gauges and count "one-one-thousand, two-one-thousand" for every decreasing foot on the gauge during free ascents.

Never take what anyone says for face value. Go out and try it. Take a group of divers. Put their hands behind their backs (to hide their watches) and have them walk a length of 60 feet at "30 feet/min" and time them. Take another group and tell them "two seconds a foot" and see what happens. The divers in the latter group will go slower and be far closer to the rate we are looking for. Play with this in the water and see what happens. Also watch what happens when divers walk alone versus walking in a group. Peer pressure can be a powerful force.

Having usable, measurable ascent rate terminology arises, no pun intended, when divers do not have an ascent line. Any working dive guide will tell you that few divers can competently stop and hang at any depth, let alone shallow depths such as 15 feet. Why do so many divers end up popping up in the last 15 feet? One answer is because they let go of the ascent line and head for the boat after their safety stop. How many divers can perform a 2 second per foot ascent rate without a line? Not enough.

Andrea Zaferes
Lifeguard Systems & RIPTIDE
www.teamlgs.com www.rip-tide.org
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