I taught a PADI Deep Diver specialty once as a shore dive at Buddy Dive, in Bonaire, to three students. For the 130 ft (3rd) dive the plan was to go to just above 130 ft right in front of the resort (easy to do) and hold depth there while we were doing the mandatory skills (this is the "narcosis test" that used to be in Dive One of the specialty). Part of the briefing was the idea that you didn't go deep just to go deep, you went deep for a purpose, for some mission, something to see for example. Our mission was to look out over the sand plain in front of Buddy Dive and estimate how many garden eels we could see. We did the rest of the briefing, about gas management, and simulated emergency decompression from a cylinder left at 20 ft, etc., and off we went. All seemed to go well. After we surfaced, we were debriefing and I asked how many garden eels they had seen. One of the guys said he'd just started counting until I'd called time and he'd gotten to 60 and then got bored. The lady said she'd estimated a little square on the bottom and counted 12 eels in it, and then estimated she could see at least 10 such squares, so she figured there were at least 120 garden eels. The third student listened to this, looked at me, and said, "Garden eels? I don't remember any garden eels." Yeah, he was narced.