From how we did for tipping in the past (group tipping), the crew didn't know how much they get & from whom. I only know what I put in, not what the others put in, unless he or she personally told me so. It's an honor system. May be that may not be effective in your opinion, but they seem to accept it & please to receive it.
I do also put comments to their service evaluation form for any improvement needed or if they did a great job.
What I meant was that because so many divers have different perspectives about tipping (e.g., an American versus an Australian), I wouldn't be surprised if the aggregate tips averaged out to a more or less constant baseline over the year. If that happens, the crew will never know from the tip amount alone that some customers felt the crew was underperforming. I think the service evaluation form is really the key here.
@chillyinCanada , I would be surprised if everyone on the Dewi Nusantara did not feel they received truly amazing service. It's my understanding that the Dewi is one of the top-rated liveaboards in the world (and beyond my budget). I suspect they are consistently booked solid. In my humble opinion, if 10% is really the norm, they should just bump the price 10% and be done with it, making sure customers know that tipping is absolutely not expected. Or raise it 5% or 2% or whatever. Their well-heeled customers will understand, and maybe even appreciate the simplified process. As divers hail from all over the world these days, the tipping thing causes nothing but confusion, as evidenced by this and so many other threads, on SB and elsewhere.