OK, real life situation -- There is a dive at our "local mudhole" called the boundary line dive. You descend in shallow water and follow a rope on the bottom which is the "boundary line" for a "no-diver zone" around a fishing/water taxi pier and go from "Cove 3 to Cove 2." This can be a very fun dive -- starts shallow, goes deepish (100' or so) and ends shallow.I really would like to know if there is a reasonable need for knowing a SAC rate, where not knowing it would be less safe.
An "average diver" should take about 10 minutes following the line to get to 100', stay at depth about 15 minutes and then take 10-15 minutes to come back up to the shallows.
While NOT an "overhead" environment, because of the "no-diver zone" (and the real possibility of getting hit by a boat or snagged by a fisherman), we all believe there is a "virtual overhead" especially in the deep area of the dive.
Which do you think would be a safer way to plan this dive? Have an idea of your average (normal) air consumption rate so you can estimate how much gas you need for your times at depth OR just wing it?
BTW, a couple of years ago an "average diver" and her buddy did this dive without any gas planning (I've heard the buddy didn't believe in it), she went OOA and went on his octo and started to the surface. At some point she evidently panicked and bolted, embolized and died. Now she didn't die because of not knowing her SAC rate -- BUT, in the chain of events, HAD she known her SAC rate, HAD she done a "quick and dirty" calculation of expected air consumption, she would have known she didn't have enough gas in her tank to do the dive. IF she had done the calculations and then concluded the dive wasn't feasible, my guess is she'd be diving today.
As I asked in a talk I gave a while ago:
HOW MUCH GAS DO YOU NEED?