While I am prejudice, for the most part Divers are crappy tippers, especially Instructors and Students (there are always exceptions though). Students because I think that they are just not aware that tipping the crew is customary and Instructors perhaps because there may be a bit of entitlement. On the otherhand, fishermen tend to more generous or are at least aware that tipping the crew is appropriate and customary, typically 15-20% of the cost of the trip. Whether Captain, Deckhand or DM, boat wages are poor and typically work out to less than minimum wage. Therefore, we can only survive and provide you with an excellent service only if our income is supplemented by tips. Additionally, and especially during winter months, I might be lucky to get one or two trips a week and even during peak season, rarely will there be a full weeks work. So we become forced to work multiple boats or jobs. Bottom line is, as a captain, deckhand or DM there is nothing you can do about weather, seas, hunting conditions or diving conditions so you damn-well better have something else going for you. On my boats you get a safe boat ride and excellent service, that's all that can be promised. So, we are ultimately a poorly paid service industry, not unlike waiters and waitresses except that we are responsible for people and lives, not food and cocktails. If you are willing to pay a gratuity for good service with your food and drink, wouldn't you want to be gracious to those maintaining your well-being and providing an excellent service?