By Karl Shreeves
One of the first things you learn about tek diving is that it’s not unusual for planning the dive to take longer than the dive itself. This is particularly true when you plan a deep dive involving multiple gases and substantial decompression. Planning a tek dive requires considering several factors that really don’t influence a recreational dive substantially.
Prudent tek divers plan a dive as a team, consulting a checklist to be sure they don’t overlook any element. A complete checklist at least minimally covers gas management, decompression, the mission, oxygen concerns, inert gas narcosis, thermal considerations and logistics. All of these topics can be remembered by recalling the mnemonic, “A Good Diver’s Main Objective Is To Live” (Good—Gas management, Diver’s—Decompression, Main—Mission, Objective—Oxygen, Is—Inert gas narcosis, To—Thermal considerations, Live—Logistics).
Although the following list is not dive specific (divers add others in each category to address the specifics of each dive), it will take tek divers through the basics. You’ll find mnemonics other than “A Good Diver’s Main Objective Is To Live” to cover the dive planning components. But I like this one because it reminds me why we plan the way we do.
Karl Shreeves is VP, technical development for PADI and DSAT, and an avid technical diver.
A Good Diver’s Main Objective Is To Live
the tekkie guide to checkin’ it twice
Do my teammates and I have enough of each gas for the planned bottom time and decompression?
Do my teammates and I have sufficient reserve planned (usually one third)?
Immediately before the dive, have we personally analyzed all the gases we’re going to use?
Do all regulators and valves work properly?
Do all cylinders have the proper markings?
Do all cylinders have a second stage at all times (except argon)?
In case of gas supply emergency, do all divers have two or more independent gas sources at all times?
What is the turn-around pressure for the bottom gases?
Is the entire team using compatible (ideally the same) gases?
How do the planned decompression and contingency decompression compare to the gas supply?
Does every diver have at least two independent ways of determining the decompression requirements on the dive?
Does every diver have at least two independent ways to determine depth and time on the dive?
Does everyone know what the mission (dive objective) is and agree to it?
Can we reasonably expect to be able to do it?
Have we simplified the mission as much as possible?
Are all team members qualified for their roles on the mission?
Can we abort the dive at any time, no matter where we are in the mission?
Does everyone agree that the primary mission is to come back safe and unhurt?
Does the dive plan keep the oxygen partial pressure within accepted limits (generally, 1.4 ata for the working phase, and 1.6 ata for the decompression phase)?
Does the dive plan account for oxygen exposure (Oxygen Tolerance Units) for previous dives as well as this dive?
Does the equipment meet oxygen service requirements where required?
Inert gas narcosis
For the depth, environment and objective, would narcosis be a significant factor?
Has the dive plan been simplified?
Do all divers have experience working at the planned depth?
If needed, do the planned bottom gases have sufficient non-narcotic helium to reduce narcosis to an acceptable level?
If using helium blends, are all team members trained and qualified to use them?
Are all team members equipped with exposure suits adequate for the planned dive duration, plus a reasonable extra to cover extended decompression?
Do divers using argon in their drysuits have ample supply?
Will divers using wetsuits have adequate buoyancy compensation and insulation to allow for suit compression at depth?
Are all suit zippers, valves and seals in good working order?
If using drysuits, what are the contingency plans for a major drysuit failure?
Who will provide what for the team in preparation for the dive?
Who is the leader/leaders?
Where will the team meet and when?
Where is the closest emergency medical facility?
Do we need surface support or support divers? Who will handle this?
Is everyone trained in first aid and emergency oxygen use and know where to find the equipment?