All the bad buddies I dove with had one thing in common: they had tendency of swimming and swimming a lot, like the water "over there" was different. So often I wanted to yell at some buddies - STOP SWIMMING!! For some reason some divers think that diving is underwater swimming; they'd just descend and swim swim swim. I don't even remember when I got separated from my buddies (well, the good ones), because I prefer to go and stay at some place exploring it. Once we're done exploring, we would point where we want to go, move towards that direction a little and stop and explore.
It takes good buddy to find a good buddy. Those who just swim and swim don't realize that they are bad buddies themselves. They often take off without looking, they get the buddy tired, they waste air, they don't see much and they don't let the buddy see much.