Interesting story. I was at Sipadan two months ago. I saw the map of the cave on the boat. It clearly was a cave, not a cavern, and they even offered a special 'cave dive', which I think involved proper cave gear for at least a DM/guide and only one or two divers, but I didn't follow up (although I did have cavern gear). The first time there we went near the mouth only, but a bit to my surprise later in the week the DM said she'd take 5 of us inside. I also declined, both at the briefing on the boat and confirmed when they went in by signals. I said I'd wait outside at 30-40 ft. The others were back after 15 minutes or so and the dive continued along the nice wall back to the much nicer shallows. I got no negative comments from anyone, including the DM. I mentioned afterwards to some of the others the dive violated 4 of the 5 basic cave diving rules but none of the pretty experienced group (but mostly tropical/liveaboard diving, no overhead training) appeared particularly phased. I'm still somewhat puzzled by this. A friend told me when I mailed him a trip report that the fact that even turtles apparently drown there should have been an obvious sign that this dive has problems. I didn't expect them to die, but my choice was clear to me and not an issue during the dive as I decided beforehand I was willing to wait outside by myself. I think there are at least two issues - not all divers recognize that some dives are potentially a bad idea, but some who do might feel pressured to do those dives anyway. Don't...