As a working DM tips range any where from nothing to $100 (so far for me). The odd thing is, I find the best divers always tip more and the divers who require so much extra care tip the least. On average here in Florida $5-10 per person is the norm. On the boat I work on the deck hand and myself split everything straight down the middle. The Captain gets his from the actual trip. We do not get paid any other way (sadly, and without us, the Captains job probably wouldn't exist). I have a few perks like, my husband can come out and dive for free anytime so long as there is an open spot for him. Crew dives every now and then to blow off some steam.
As a DM, I'm here to tell you, we work hard. Not just loading and unloading all your things, making sure the energy level stays high on the boat, feeding you, and tending to your every little whimper.... We also have to babysit some of you (you know who you are)
. It is my job to work out the dive plans (although I expect you to have your own, mine is a back-up plan if I see your exceeding the safety zone), I keep a close eye out on everyone while still hooking you up with the best the reef has to offer. I usually have any piece of equipment standing by waiting for something of yours to break so I can jump out with the big save a dive kit and fix it. Should your injury yourself, I've taken several expensive classes to make sure you are as safe as we can get you until more help arrives. When you get sea sick, it will be me coming to your rescue to hose you off if you don't make it to the stern. I'll be the one holding a few ice chips for you to suck on to rinse out the puke taste and still keep you hydrated. When you forget to pick up your mask off the boat deck, I'll be the one who snatches it up before anyone steps on it. When your getting on the boat and drop something back into the ocean, it will be me racing to whatever depth to fetch it. When your sitting there staring at your new computer completely clue less, I'll be right there to break it down for you.
I have to pay very costly insurance every yr to protect both you and myself and keep up with the latest dive gear. The great DM's do all this everyday without a single person catching on just how hard we really work. It is our job to keep the "un-fun" stuff away from our customers far behind the scene.
This is my job and I love ever second of it! On my boat, the Captain says nothing about tipping us or even that we work for free. We have a small tip jar for people to throw $$ in. We do it this way so people don't feel awkward handing it to us (I don't think I'll ever get use to that weird feeling of someone handing me money, I like the jar method).
BTW, we don't stand around the dock complaining about our tips or lack of them. I'm happy if I make enough to pay for my gas to drive down.
If your DM/crew is good, tip them! Don't hold the weather, temp,current or viz against them.