raviepoo once bubbled...
I think $10 per day for a liveaboard verges on abuse. Think about it. On a liveaboard you might do 4 - 5 dives a day. If you did that on a charter boat your $10 per day tip would break down into $2 per dive - cheap, cheap, cheap. And I'm not even taking into account all of the other service the staff provides during the 24 hours a day you spend in their care.
The absolute MINIMUM I would consider tipping is 10% of the cost of the trip unless the crew is rude and negligent. For good service I give more. On a $1800 7 day liveaboard trip with good service I would probably tip 15% or $270, a far cry from the 70$ indicated by some others in this thread. The MINIMUM tip I would consider would be $180.
Liveaboard crews work like dogs. They help you in and out of the water. They fix your faulty gear. They are responsible for hauling you out of the water if you do something really stupid. They scrub all the boat's filthy places. They fill your tanks so you can do five dives a day. They fix engines. They mop up vomit. They muck out the heads. They take turns staying up all night, navigating and/or driving the boat while you sleep off the last evening's rum punch. They wake before the sun to be sure that your coffee is ready in the morning. They deserve both respect and compensation for all of their hard work.
Trust me, if you are tipping out $10 per day to the staff of a first class liveaboard they WILL remember you - as a cheap-skate. They might not be so eager to mop up your diarreah the next time you come aboard.
Honestly, if you can't afford to tip the staff you have no business being on the boat in the first place. Save your pennies and find a hobby you can afford.