Experienced Divers and OOA emergencies

[Brian Sharpe]

And in the range of 100 ft to 130 ft you should rely on the Rule of Thirds, where you use 1/3 of your total SPG pressure on the outbound leg of your dive, and the second 1/3 to return to the anchor line, saving the last 1/3 as a reserve. Your tank size should be determined to meet this Rule of Thirds, large enough so that 2/3 of it meets your needs for the dive.

Great advice - thanks!

 

[b1gcountry]

Great advice - thanks!

Not entirely. If the anchor itself is in 100-130', then you very well may use more than 1/3 of your tank getting two people back to the surface from the anchor line. From 120', it could take more than 40cf to get two stressed divers back on the boat. If you plan on doing these sorts of dives, you need a little more planning than just the rule of thirds.

Tom

 

[Alex777]

I have never had an "OOA emergency" but my wife / buddy and I will frequently swap gear underwater to equalize our air consumptions. We will both end the dive with some air remaining but, often, we are in each other's gear. (We have the same weighting requirement.)

 

[Gombessa]

Not entirely. If the anchor itself is in 100-130', then you very well may use more than 1/3 of your tank getting two people back to the surface from the anchor line. From 120', it could take more than 40cf to get two stressed divers back on the boat. If you plan on doing these sorts of dives, you need a little more planning than just the rule of thirds.

Tom

Exactly. You should calculate your rock bottom for the dive, subtract that from your total tank capacity, and then plan the dive with the amount remaining.