PADI Deep Diving Techniques & Planning 5 — Questions and Answers
Question 1: You are planning a deep dive to 100 feet in a location with a known thermocline at 60 feet. How should this affect your planning?
- The thermocline has no impact on dive planning
- Plan for significantly reduced water temperature below 60 feet and pack appropriate exposure protection (Correct answer)
- Avoid diving past the thermocline entirely
- The thermocline will reduce nitrogen absorption and allow longer bottom time
Correct answer: Plan for significantly reduced water temperature below 60 feet and pack appropriate exposure protection
Thermoclines mark sudden temperature drops, requiring divers to carry adequate thermal protection to prevent hypothermia at depth.
Question 2: What is 'residual nitrogen' and how does it affect planning for a second dive?
- Nitrogen left in your tank; it must be refilled before a second dive
- Nitrogen remaining dissolved in body tissues after a dive; it reduces NDL on subsequent dives (Correct answer)
- Nitrogen bubbles visible in the water after exhalation
- Nitrogen locked in wetsuit foam that affects buoyancy
Correct answer: Nitrogen remaining dissolved in body tissues after a dive; it reduces NDL on subsequent dives
Residual nitrogen is absorbed gas remaining in tissues after a dive, which shortens the no-decompression limit available during any subsequent dive.
Question 3: Why should deep dives always be conducted as the FIRST dive of the day when planning multiple dives?
- Deeper dives are more tiring so should be done when energy is highest
- Residual nitrogen from earlier shallow dives reduces available NDL at depth, increasing DCS risk (Correct answer)
- Visibility is always better for deep dives in the morning
- Boat captains prefer to go deep first for scheduling purposes
Correct answer: Residual nitrogen from earlier shallow dives reduces available NDL at depth, increasing DCS risk
Starting with the deepest dive ensures minimal residual nitrogen in tissues, maximizing available NDL and reducing decompression sickness risk.
Question 4: A deep diver notices their air consumption rate is twice as fast as in shallow water at the same exertion level. What is the BEST explanation?
- The regulator is malfunctioning
- Increased pressure at depth compresses each breath, requiring more gas molecules per inhalation (Correct answer)
- The diver is hyperventilating due to narcosis
- Cold water causes faster metabolism and higher breathing rate
Correct answer: Increased pressure at depth compresses each breath, requiring more gas molecules per inhalation
At greater depths, ambient pressure compresses gas, so each breath delivers the same volume but contains more gas molecules, depleting the tank much faster.
Question 5: When using a dive computer for a deep dive, what should a diver do if they accidentally exceed the planned maximum depth?
- Ascend immediately at emergency ascent speed
- Continue the dive normally; the computer will automatically adjust all calculations
- Monitor the computer's updated NDL and adjust bottom time accordingly, then ascend normally (Correct answer)
- Surface immediately and call for emergency assistance
Correct answer: Monitor the computer's updated NDL and adjust bottom time accordingly, then ascend normally
Modern dive computers recalculate NDL continuously based on actual depth; divers should monitor the updated figures and ascend conservatively within the new limits.
Question 6: What is the recommended action if a diver feels the effects of nitrogen narcosis severely impairing their judgment at depth?
- Breathe faster to reduce carbon dioxide buildup
- Ascend to a shallower depth until symptoms improve, then reassess whether to continue (Correct answer)
- Continue the dive while buddy keeps close watch
- Descend further to equalize pressure on the nervous system
Correct answer: Ascend to a shallower depth until symptoms improve, then reassess whether to continue
Ascending even a short distance significantly reduces narcosis effects because the partial pressure of nitrogen decreases with shallower depth.
Question 7: Which pre-dive check is MOST critical specifically for deep dives compared to shallow recreational dives?
- Mask fit and strap condition
- Verifying adequate gas supply and gas-sharing capability with buddy (Correct answer)
- Checking fin strap buckles
- Confirming wetsuit zipper is fully closed
Correct answer: Verifying adequate gas supply and gas-sharing capability with buddy
At depth, gas consumption is much higher and out-of-air emergencies are more dangerous, making verification of sufficient gas and working octopus/alternate air source critical.
PADI Deep Diving Techniques & Planning 5
You are planning a deep dive to 100 feet in a location with a known thermocline at 60 feet.
How should this affect your planning?