I don't see him as negligent, just that having to have max ratios isn't a good idea. I do not know if this was a DSD or if he was guiding.
I've made mistakes while teaching. Haven't you?
I'm not ready to throw the instructor conducting the DSD/Try Scuba under the bus, unless he only had 2 people, which I believe he did not.
I feel that the agencies with 1:4 ratios for DSDs/Try Scuba experiences are negligent. I also feel that for proper instruction, agencies with 1:8 ratios are negligent. Instructors who push back against their employers for ratios are simply finding themselves out of a job, and in some cases, in a serious jam. So much for living the dream.
The instructor's account of the events (Spanish, auto-translated to English via FB), posts #18-19, is in this thread. Here's my brief summary pulling from that account:
- 40 minute class explaining diving theory, diving practices and equipment
- equipment setup by instructor, but had divers open tank, do safety checks under his supervision
- two DSD's and one OW
- after buddy check, divers went down to 1.5m and did exercises (likely mask clearing, regulator purging, etc.?)
- first dive went well
- instruction reiterated during surface interval
- second dive was 36 min
- at 14 min, 4m, Rocio (woman in incident) signed she wanted to go up. Instructor asked her why and she indicated she was having a laughing fit and he signed back it was okay to laugh into regulator and asked if she wanted to cancel (since they were next to the boat) or continue to follow. She indicated she wanted to follow.
- all three divers had 110 bar, so nothing to indicate one diver was more distressed than the other
- dive was by a buoy with max depth of 9m
- dive continued for 18 min, going away from the buoy
- upon return to the buoy, instructor asks divers if they're okay and the respond yes
- instructor looks for boat and when he turns around, Rocio is missing
- instructor asks other students if they've seen her and they indicate no
- instructor takes other students on reverse course and is unable to find Rocio, so surfaces with remaining two students
- instructor tells boat he's missing a diver and asks if they've seen bubble trails
- boat points out to a bubble trail and he descends again to search, but finds it's not her
- upon surfacing, he finds Rocio being brought to the boat by a colleague who had found her with mask on and no regulator in her mouth at 6m
- O2 administered, Koh Tao Rescue contacted, and two client divers on the boat were doctors helped in the emergency
- instructor followed Rocio from Koh Tao, to Koh Samui, to Bangkok
- instructor, two accompanying divers, and others from the dive op gave accounts to police (It would be nice to see these accounts.)
- instructor contacted consulate and family
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I'm only AOW, so I don't teach, but I know what you're saying.