My very first Divemaster Training (DMT) dive. I buddied with a DLD diver that was tagging along on an Open Water course. About 10 minutes into the dive as I watched my buddy pop to the surface and students scatter in every possible direction I was really questioning my decision.
Got "yelled at" underwater for the first time which is a real experience (although in the end after some explanation above water the reprimand was withdrawn).
Amazingly enough, this dive ended up being the worst one of my entire DMT experience. How's that for luck?