One of the most tragic body recoveries we’ve ever had to perform was that of a diver who ran out of air in Devil’s Eye while searching for his buddy. What made this tragic was that the buddy, who had followed procedure and exited when he could not reunite with the victim before hitting a safe turn pressure, was patiently waiting for the victim at the surface — as he should have. How can you keep this from happening to you?
Among the many skills we teach during Cave Diver training is how to determine how much gas you have available to search for a missing team member. Here are some approaches you can take, both entering and exiting the cave.
Going into the cave
If you are going into the cave, there are at least two different approaches you can use. Here is the more conservative of the two:
- Let’s say your starting pressure was 3,600 psi and you plan to turn at 2,400.
- Half way into the cave, with 3,000 psi remaining, your buddy goes missing and you have to search for him.
- Your usable (penetration) gas was 1,200 psi. You’ve so far used 600 psi. Add the two together; you get 1,800 psi.
Many instructors teach that you should abandon your search and begin exiting when you reach this pressure (1,800 psi). As you still have3,000 psi, this leaves you1,200 psi with which to search for your team mate. It also provides more than twice the gas you theoretically need to exit; the additional gas will be available to help solve unforeseen problems.
But what if you feel this amount isn’t sufficient? What if the diver you are looking for isn’t all that experienced. or is someone like a spouse or child? How close can you afford to cut it? There is another approach that affords more gas to search with, yet still adheres to the Rule of Thirds…barely. Here it is:
- As you’ve used 600 psi to get to this point, you need to be back at this same point and exiting with twice the gas you theoretically need to get out of the cave, or 1,200 psi.
- This leaves you 1,800 psi with which to search for the missing team member.
Bear in mind this method allows no additional reserve other than adhering strictly to the Rule of Thirds.
Exiting the cave
What happens if you have already hit your turn pressure and are exiting the cave when a team mate goes missing? How do you know how much gas you can safely use to look for him? If you are in a cave that has distances clearly marked on line arrows and is fairly consistent in depth, you may be in luck.
- Using the same starting and turn pressures as in our previous examples, let’s say you turned the dive at a maximum penetration distance of 1,500 feet.
- Somewhere in the vicinity of the 1,000-foot line arrow, your buddy goes missing.
- As this was two-thirds of the way to your max penetration, it’s reasonable to assume you used roughly two-thirds of your useable gas, or 800 psi, getting here.
- This suggests you will need to be back to this point and exiting the cave with no less than twice this, or 1,600 psi.
- As you still have 2,000 psi remaining, this gives you 400 psi with which you can conduct a lost-buddy search before you need to begin your exit.
Remember that, as with the second method outlined for searching for a missing diver while going into the cave, this method affords no additional safety margin other than adhering strictly to the Rule of Thirds.
How much of an additional safety margin do you need?
As with anything in cave diving, you are foolish if you push gas management to it’s absolute limits. You have to make additional allowances for factors such as:
- You are going to be stressed and, most likely, breathing faster.
- Line arrow distance markings may not be entirely accurate.
- If the cave gets deeper as you get closer to the entrance, you will need to allow for greater gas consumption as you approach the exit.
- You may have to allow time and gas to deal with additional issues during your search, such as low vis and/or a buddy who is trapped or entangled, or low on gas.
You may also have factors that work in your favor, including:
- A cave that gets shallower as you approach the exit.
- Flow, which can substantially reduce gas consumption during exits (a savings, however, that is not easily quantifiable).
Overall, though, you are going to want to allow additional safety margins. How much of a margin? It is going to depend entirely on the situation. You will have to rely on your experience and judgment in making this determination — just as you would in a cave with no distance markings, or if you failed to note the distance at your maximum point of penetration. Just remember that you are of no use to anyone if you are dead.
Also bear in mind that, unless your buddy is entangled in guideline or trapped in zero vis, it’s most likely a simple buddy-separation situation and, if you don’t connect with one another in the cave, odds are you will meet up on the surface. That’s not worth dying for.