I was always taught u tip a boat crew whether this is a fishing boat or a dive boat. Instructors/boat crew are providing a service where pay is minimal, its like do u not tip the delivery guy or 20% to a waiter in a restaurant? Less if service is bad obviously. Pay on both is minimal and tips is where u make up the difference. I tend to give $10 for a 2-tank dive, If the divemaster/instructor is not attentive and friendly id give less. They help u with ur gear, some will wash ur gear and hang it till the next day. I understand im not rolling in the dough but if i can afford the vacation im on or the price of the boat $10 to a guy making $40 a day sure as shit isnt killing me! If it is stick with shore diving u dnt have to tip ur buddy then. I live in NY so maybe im used to tipping but i know when i delivered pizza for $2 hr tips is what i relied on to make my main bulk of the money. $100 for 4 hrs of work, 1998’ im talking too, i guess i made alot in tips! Sorry im a tipper, i tip my bartender too. I would tip more if i was a student who needed the instructor to spend extra time on underwater issues as well. Tipping on a course id say a minimal of 10% unless the instructor was a total jerk. Plus if it is a dive shop Im gonna use and deal with i dnt want to be know as the cheap guy who stiffs his instructors either.