If it was down here in South Florida you heard the "tacky" announcement there is a reason for it. There are tourists (international) here that are not used to tip much and tipping on a boat is outside what they are used too. Even many restaurants on for instance Fort Lauderdale beach add 15-20% on ALL checks, so watch out.
I tip the DM but not the Captain as per reasons previously stated, he is the owner or is paid for his license. I also don't give the tip to a Captain and tell him to forward it to the DM since there are those that will pocket the money them selves.
To tell a DM to get out of the way is IMO wrong, tell em how you want it and they will let you do it your way as long as it is safe (they are locals and know about local conditions). Even if you tell them to not help you at all a normally good DM is still watching your back and catches you when you fail/fall.. i.e. all DMs are earning their tip and most are not paid at all by the boat.