I used to have a regular buddy who had the bad habit of slipping a little behind and above me as we dived. He felt very comfortable there because he could keep an eye on me so easily. On the other hand, I developed a quite literal pain in the neck from trying to find him constantly. After a talk, we reached the point that we stayed where we could easily see each other with a glance any time we wanted.
If you are in a situation where you are diving with lights, your dive light can make things very easy for you, especially if you are in a single file situation. If one diver is the lead diver, he or she should make sure the light is usually in a place where the following diver can see it. The following diver then makes sure to pass his or her light beam just below (or next to) that beam every 20 seconds or so. that says, "I'm here, and I'm OK." If the lead diver senses that it has been too long since that signal was seen, covering the light with the hand not only allows the other diver's light to be seen, it reminds the other diver to show the light. If you are not in a lead/follow situation, each diver should make sure to play the light beam near the buddy's light regularly.
If you are in a situation where you are diving with lights, your dive light can make things very easy for you, especially if you are in a single file situation. If one diver is the lead diver, he or she should make sure the light is usually in a place where the following diver can see it. The following diver then makes sure to pass his or her light beam just below (or next to) that beam every 20 seconds or so. that says, "I'm here, and I'm OK." If the lead diver senses that it has been too long since that signal was seen, covering the light with the hand not only allows the other diver's light to be seen, it reminds the other diver to show the light. If you are not in a lead/follow situation, each diver should make sure to play the light beam near the buddy's light regularly.