I would imagine that decision would rest with the DM, but that most would err on the side of caution and the judgement of the crew at the surface. They just need to figure out what they need to do in order to round up their divers. I have been involved in a few of these and I know that Jeremy wants everyone close together to facilitate pick up and entry into the boat. Usually he instructs us to hang onto one-another's tank valves. I haven't been on one of these dives with his new DMs since he pretty much stopped leading dives, but I would have to believe he's told them that is how he wants it done.
