Can you assume that? I once went on a liveaboard where another passenger told me the captain/owner of the boat took a cut of the tips. I was a bit shocked but didn't have a chance to investigate further at the time.
I've seen rumors to that effect in these threads. I have no idea, but I suspect it is a rare boat that does so.
Unless I get truly exceptional service from someone, I either tip in an envelope to all or, for day trips, give it to the DM. I assume there is some agreed upon tip-sharing program and don't try to second guess that by tipping every single person on the boat with my assumptions of what each person "deserves"