Thunderstorm Approaching Mid-Class
You are leading a 50-minute deep-water bootcamp with 18 participants in an outdoor pool. Water 27 °C, air 31 °C, light breeze. Twenty minutes in, a participant points to darkening clouds to the west. Your phone shows a severe thunderstorm warning with lightning detected roughly 15 km away and moving toward you at about 40 km/h. The facility's written policy says to clear the pool when thunder is heard or lightning is seen, and to wait 30 minutes after the last thunder. No thunder has been heard yet and no lightning is visible to the group. Several participants say the storm will 'probably miss us' and ask to finish the last 15 minutes. The pool has no indoor backup and the deck has a metal shade structure.
1. Should you clear the pool now or continue? Justify using the policy and the risk picture.
Read the worked answer
Clear now. The policy's 'thunder heard or lightning seen' is a minimum trigger, not a ceiling; a professional may act earlier on credible information. At 15 km and 40 km/h, the storm is roughly 20+ minutes out, which is within the window where the leading edge can produce lightning before thunder is audible or visible. Continuing for 15 minutes would put the group in the water as the risk arrives, and evacuation itself takes time. The decision is defensible on duty of care even though no one has yet heard thunder.
2. Describe the evacuation you would run, including where people go and why the shade structure is or isn't acceptable.
Read the worked answer
Use a calm, scripted announcement: class is ending, exit at the nearest steps/ladder, leave equipment. Account for all 18 by name or headcount at a designated muster point. Move people away from the metal shade structure and out of the open deck into a substantial building or vehicle; metal shelters and open structures offer little lightning protection. Keep everyone out of and away from the water. Assign a co-instructor or responsible participant to the muster point while you sweep the pool and deck.
3. When may the pool reopen, and how do you handle the group's disappointment and the documentation?
Read the worked answer
Reopen no sooner than 30 minutes after the last thunder is heard (or per facility policy, whichever is stricter), restarting the clock with each subsequent thunder. Communicate the rule and the reason briefly and without debate; offer a credit/reschedule per facility practice. Document the time of clearance, the trigger (warning plus observed conditions), the muster count, and the reopening time. Note participants who objected so the pattern is visible if it recurs.