The dive plan had a good rhythm: morning, twilight, morning.
Four of us were going to Cozumel for the weekend. I wanted three two-tank boat trips, one each day, with a private boat and one divemaster for the group.
The first trip was booked for Friday morning. Saturday would start later with a twilight dive. Sunday went back to the morning schedule. I also wanted to fit in a night dive if the second tank on the twilight trip could happen after dark.
Getting there took a few rounds of email. I first asked for every available morning, afternoon, evening, and night option. The operator explained that each boat trip took about four hours and that twilight timing depended on sunset. A group of four was enough to arrange the Saturday trip.
I sent back the schedule I wanted. The private boat already came with a divemaster, so there was no reason to add another guide. That removed one extra piece from the booking.
The operator confirmed two morning trips and one twilight trip. I asked them to hold the space and completed the reservation. That left me with the itinerary I wanted.
Friday morning would open the weekend. Saturday changed the light and left a chance that one tank might count as the night dive. Sunday morning put everybody back on a boat one more time.
The reservation did not promise that weather, water, or travel would cooperate. It did give four divers a clear place to start when Friday arrived.