"Will this be miserable for the rest of the crew?"....probably. 10 people going, 1 has a special interest which requires time and of course,location. So everyone twiddles their thumbs while he is diving and then, of course, will be expected to lend a hand and also keep an eye out while he is diving. Depending on the other crew members, could work. If it were me, he can arrange rendezvous diving and we'll tell him where to meet up with us later. Just have a feeling this is not going to work out.