shurite7:I would say the inconsiderate person was the worst problem. If people are looking sea sick don't over extend the last dive while everyone else is onboard ready to go.
I'm not too worried about people being inconsiderate, that's a matter of manners not safety. If they've paid for 2 45 min dives(or whatever), they should be able to dive their allotted time. It's not their problem that someone else is getting sick. I don't really allow people to extend their time beyond the planned times, mainly because I run multiple trips in a day and have a schedule to keep.
I always cringe when people start a trip off by saying how they get sick everytime they go on a boat: try shore diving!