They use a numbered tag system that works well. They load your gear on the boat (you assemble it on the dock) and put a numbered tag on it. Then, they roll call for divers to board the boat. At the end of the dive before leaving the site they again do a roll call by number. All accounted for, on they go to the next site (or back in if it's the last dive). After the last dive you have to actually take the tag off your tank and give it to them when your name is called. The system seemed to work and makes sense for any op who takes out that many diver. There was a couple on one dive who 10 min after the time to be back were still not onboard or in site. The DM jumped in with mask, fins, snorkel to take a look around. They popped up about 5 min later but over at the wrong boat. He swam a line out to them to help them back and they were repremanded onboard. When you've got a 40 min trip back and an afternoon dive going out 45 min after that, nobody took kindly to these two holding us up for almost a 1/2 hr. They weren't back on the boat for the afternoon dive.