I make it easy, tipping 20%,
Many people do tip a percentage when diving. Consider the following examples - they are all highly regarded dive ops in Cozumel providing many of the same benefits (valet service, gear storage, fleet of boats, etc..)
Dive shop A in Coz charges $95 per 2 tank dive before taxes. A 20% tip is $19.
Dive shop A has no multiple dive day discount. 5 days diving is $475 which would garner a 20% tip of $95.
Dive shop B charges $75 per 2 tank dive before taxes. A 20% tip would be $15.
They also have no multiple dive day discount so 5 days diving is $375 which would be a $75 tip
Dive shop C is pretty high at $110 for a 2 tank dive - 20% tip of $22.
With their 5 day discount the total would become a pretty low $325 which would be a $65 tip or $13/day.
My question would be, if these dive ops all provide a similar service/experience, does one warrant more or less of a tip just because they charge a different price?
My answer would be no and it's the reason I don't do a percentage but simply provide a $10-15 tip for a 2 tank dive.