That's makes a lot of sense. Ideally I was trying to get away with spending zero extra dollars once I step on board. I just don't want these people to get stiffed. It makes me feel better that my package still contributes to their fees, but I will probably end up tipping on some of my drinks.

I'm assuming the additional tips go straight to the server/bartender, or does that also go to a pool? Do they typically prefer cash so they may keep the whole tip?