Is it just me or does 35-40 ft seem a bit deep for a DSD?
For better or worse, the PADI standard for an OW DSD dive is a maximum depth of 40 feet. I can't speak for other agencies. And, I have some difficulty with the idea of taking a DSD participant to 40 feet, even in warm, clear water. But, that is done, and regularly it seems. And, nothing 'bad' happens - right up until something 'bad' happens, which more often than not seems to occur when a DSD participant is left alone underwater.
I was on a charter in St. Thomas in December with family, and some friends of family. Our family group included 4 certified divers, and 2 DSD participants. And, there were 4 other divers on the boat. The certified divers buddied up and swam around the site, while the Instructor completed a DSD experience for the DSD folks. Toward the end of our dive, as my wife and I swam back to the area near the boat tie-in, I saw the DSD folks swimming around (at a depth of ~40 feet), with the Instructor nearby, thoroughly enjoying themselves - they were literally grinning underwater. Afterward, they both said they had 'an absolute blast', and one of them - my son-in-law's father, now wants to get certified. Nominally, it was exactly what DSD is all about - people experiencing the beauty of the underwater world - without incident - and wanting to continue.
I cannot conceive of a set of circumstances under which the standards for DSD were adhered to in conducting that experience. But, I had not set it up, I was on the trip as a diver, not an Instructor, and I didn't say anything afterward - either to the very elated DSD participants, or to the Instructor. I had the definite impression that this approach was 'usual and customary', though. I couldn't / wouldn't do it. But, apparently many others do.