scubasherry:We tipped the boat captain and the DM each their own tip. We gave our boat captain $10 per day he was a really cool guy. We tipped 5 per tank for the DM's.
I tip both DM's and taxis. This is the best way to be sure your money is going to the people doing the work without most of it going to the owners.
BTW, I am not really ripping the owners. In many cases, they are doing all they can to keep their business going, but you will not believe how little of what you pay for a dive gets to the "grunts."