There’s only one component that isn’t a "part" that can screw up a perfectly planned dive.... The final mental checklist of your own gear! Was diving a dry suit and got interrupted by a gabby neighbor as I was getting gear on for a dive off a dock. Just as I took the big step off the end of the dock I started to check off the items I always mentally check off prior to "committing" to the dive. As my fin hit the water I got to "dry suit zipper" on my check list..... Needless to say that my and my "buddies" Buddy Check skills got some quick remedial training. If interrupted doing your equipment check, start from scratch. The time to do your checklist is PRIOR to the LAST item that should be "Commence Dive".