I had an experience with a team of five in Mexico. Despite the fact that we were all experienced divers and that the dive itself was not particularly demanding, we experienced a team separation (which was in part my fault). Going back over what happened afterwards, it was multifactorial, due to the second-to-last diver hitting thirds right as we got into a section of cave with some tight zigzags, which made it harder for me to be sure the guy behind me WAS behind me, and it was hard for him to be sure the guy behind HIM was there. When he realized that guy had stopped, he went back to see what had happened, and opened even more space between us. I let an unacceptable amount of time go by before I realized HE was gone. We all got back together, and nothing bad happened, but I will never do that again.