I generally tip what I can afford. Being retired, I live on a fixed income. I actually have to work part time so that I have the opportunity to travel.
When I do travel, I have a budget that I need to follow. With the current exchange rates, my Canadian dollar is at least 30% less than the value of a U.S. dollar, or in other words, my trip costs at least 30% more, as everything is in U.S. dollars.
Some trips the divemasters and boat crew get healthy tips, while on other trips unfortunately not quite as much. I do refer other divers to my favourite resorts, sometimes bringing the resorts much needed business.
Divegoose