Even when I am not teaching, I find myself watching the group both on the boat and underwater. I try to buddy with the newest diver, this most often relaxes them. Underwater, I position myself so I can react to a problem. For example, if I see someone wide eyed or breathing fast, I'll be close. Another item is my groups comfort. If I have a group of divers on an island, I make sure they know that drunk or hung over divers will not be allowed on the boat. I make this clear at the orientation meeting before the trip and so if I see someone not in condition to dive, I'll speak to them privately. So far, in 25 years as an instructor, it has worked well.