When to Turn Around on a Dive

[miketsp]

Amen to that brother!

To the OP, Check out NWGratefulDiver.comNWGratefulDiver.comhttp://http://nwgratefuldiver.com/articles/gas.htmlNWGratefulDiver.com

Of course the other articles that other Bob has written are worth reading as well.



Bob
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I may be old, but I'm not dead yet.

Wow, I read through that and all I could think of is that these calculations are MUCH easier in metric..

 

[00wabbit]

I use an app called ScubaCalc to calculate those turn pressure for me. I understand all the math behind it and can do it if I need to but the app helps a ton and gives your turn pressures for various depths so you can make a little table to follow.

 

[dmoore19]

Because that is what you are used to.

Wow, I read through that and all I could think of is that these calculations are MUCH easier in metric..

 

[tattooedjeeper]

I use an app called ScubaCalc to calculate those turn pressure for me. I understand all the math behind it and can do it if I need to but the app helps a ton and gives your turn pressures for various depths so you can make a little table to follow.

I have the Scuba Calc app as well as one called RB Planner. They're both easy to use and you can quickly do the calculations for you and your buddy on the spot. Just to be safe, I also add a few hundred psi "buffer" to the calculations for Scuba Calc when i use it.

 

[boulderjohn]

Bonaire is the perfect site to follow the rule of halves for dive planning. bradells mentioned it above. Note your starting position and depth (let's say a boat mooring or distinctive coral at 15 feet), drop to your deepest planned depth, and begin the dive into the current. You can stay at that depth or start working your way shallower. You and your buddy turn the dive at an agreed upon PSI. If you are getting gradually shallower on the way out and will get gradually shallower on the way back, halves works fine. Otherwise, you will want to move your turn point a bit in either direction. Make sure you get to the depth you had noted (in this case, 15 feet) before you have returned completely, and you will run into your starting point. When I was in Bonaire (only once), I turned my dives at 1,500 PSI and usually got back to the starting point at about 1,000 PSI because of the decreased depth and the fact that i was coming back with the current. This allowed me plenty of gas to poke around that area before surfacing.

The important thing about using the rule of halves is that if you miscalculate, you can go to the surface, with the only penalty being a longer surface swim to your exit point.

 

[freewillie]

My wife and I recently went on our first dive trip. It was to Bonaire. I listened to the pre-dive instructions which included the approximate time for the dive. Trouble was that my wife and I certainly reached 1/3 and even 1/2 of our initial tank pressure before the turn around. We were very anxious about going back on our own. We later learned that (a) going shallow greatly increased our dive time remaining, and (b) we could always surface and spot the boat. This was greatly comforting. However, I must say that I'm still confused about whether or not I should be mostly focused on psi or dtr to determine when I should turn around. How could I have missed something so basic in my OW training???
Fred

Many posts with great advise so far, but would agree that most dives are going to be turned around at a certain PSI.

You didn't really indicate if these were guided dives or a boat dive where you explored the reef on your own with your buddy (wife). If the former is the case then you should have been given specific instructions during the briefing that the guide and group are going to head back to the boat once a certain predetermined PSI is reached by the first diver. Doesn't matter if you are well above that, first diver to turn around PSI and whole group needs to head back. If that is the case then it is your responsibility as a diver in that group to alert the guide that you are at the turn around PSI. If you are diving on your own then the briefing dive times are just an approximation to what most divers can expect for bottom time. Since that time can vary based on skill, depth, exposure, exertion, current they are supposed to be just that, approximations. You and your wife should have determined when you were going to head back to the boat and at what PSI. You generally want to be back and the boat with enough air left for a 3-5 min safety stop and be left with over 500 PSI.