Professional divers will also have their logbook available so that the operator can assess your experience level. This is often the difference between being taken to a shake down dive site, which is shallow and limits the rest of your days diving, or being taken directly to the adventure sites. Last but not least tell someone back on shore where you are going and what time you expect to be back, that way if anything happens. Emergency search procedures can start immediately. Also let them know which operator you are going out, valuable time can be saved in the event of an accident.
Boats are finite creatures, bring the minimum amount needed for the day.
Personal non-dive equipment should be in a separate bag and stored in the dry area, dive gear in the wet area. Put items like your logbooks wallet and keys in sealable plastic bags, just in case your bag gets wet. On board the dive boat there is one Supreme Being, who is above all bar none, meet the Captain. They have the responsibility of your safety and most take it seriously, so listen and respect their decisions. Getting on their good side always ensures a good day out.