Low Air, Cold, and a New Computer on a Shore Dive
You are the divemaster leading a shore dive for six certified divers at a temperate site with a maximum depth of 18 m and visibility of 8 m. Water temperature is 18 °C and a mild longshore current is running. The group is in three buddy pairs. At 20 minutes, Diver A-who has 12 logged dives and is using a new dive computer for the first time-signals 70 bar and shows you the computer reading. A's buddy, Diver C, has 150 bar. Two minutes later, Diver B, in another pair, is visibly shivering with pale lips and is wearing a 3 mm wetsuit; B has 110 bar. The exit is about 80 m away and the current is slightly against you. You have 170 bar. Surface support is one shore-based observer with no second divemaster. You must decide whether to continue, split the group, or ascend.
1. What are your immediate actions and signals in the first 60 seconds?
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Priority order: confirm the two problems are real, keep the group together, and start a controlled ascent before either problem worsens.
- Acknowledge Diver A's 70 bar signal; have A and C stay together and show you their SPGs. At 18 m, 70 bar in a typical 11–12 L cylinder is enough for a normal ascent and safety stop, but not for continuing or a delayed ascent. A's new computer may explain a gas-planning error; do not assume it is wrong.
- Signal Diver B and B's buddy to come to you. B's shivering and pale lips at 18 °C in a 3 mm suit are early cold-stress signs, not just discomfort. Cold increases breathing rate and gas consumption and can impair judgement.
- Signal 'ascend' to the whole group, keep buddy pairs intact, and set a slow ascent (max 18 m/min) with a safety stop at 5 m if gas allows. Do not split the group: you are the only professional in the water, and two groups would create two supervision problems. A should not ascend alone; A and C stay together.
2. Should you send Diver A and C to the surface while you continue with the rest? Explain using supervision and gas-planning principles.
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No. The tempting solution is to send A and C up as a buddy pair and continue with the other four, but it fails both supervision and gas planning.
- Supervision: You are the only divemaster in the water. If you split, you have one group of four with you and one pair surfacing without professional oversight. A is inexperienced (12 dives) and task-loaded with a new computer; C has gas but may not have the experience to manage a problem at the surface. The shore observer is not a second divemaster.
- Gas planning: A's 70 bar at 18 m is a turn pressure, not a continue pressure. A normal ascent from 18 m plus a 3-minute safety stop at 5 m takes roughly 40–50 bar for many divers, leaving little margin for a delayed ascent, current, or buddy problem. B's 110 bar is adequate, but B is cold and shivering; cold can escalate quickly.
- Judgement: Two independent stress factors-low gas and cold-mean the dive objective is no longer worth the risk. End the dive for all, ascend as buddy pairs, and keep the group within sight if possible.
3. What follow-up do you give A and B after the dive?
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Debrief with facts, not blame. For A: review the computer's gas display and the dive plan; ask whether A understood the reserve pressure and turn pressure. A's 70 bar at 20 minutes suggests either higher-than-expected consumption or poor monitoring. Recommend a supervised dive with an instructor or experienced buddy to practise gas monitoring, and suggest a larger cylinder or shallower profile until consumption is understood. Do not label A as unsafe; the new computer may have distracted A. For B: check for continued shivering, pale skin, confusion, or clumsiness; if these persist, treat as cold exposure and seek medical advice. Review exposure protection: 18 °C in a 3 mm suit is marginal for many divers, especially with a long surface interval or current. Recommend a thicker suit or hood/vest. Log the incident internally, and if this is a course, inform the instructor. Also review your own briefing: did you state turn pressures and cold limits?