I have dived with just such an operation in the Bahamas. The husband and wife most definitely owned the business and acted as divemasters, captain and crew--at least on the trips I took with them. If I recall, I did the same as you. If I also recall, they charged a bit more than other shops, the premise being that they offered a premium service. So I felt good about paying what they charged, and I even tried to spend some extra money in the shop. But I would have felt awkward handing the owner of the shop a "tip" per se. This was a few years ago, though, and many SB threads on tipping ago. It's probably apparent from my comments that I have given the issue of tipping a lot of thought. The owners were American, and the Bahamas, being pretty much an extension of Florida (oooh, did I really say that?) receive a steady stream of American visitors. I think that if I were to return, I might just ask him to add a line on the final bill for a gratuity or service charge.