I have a small power boat, domestically built, that I want to use for something like an airbnb. The boat is going to be on a mooring and not moved. My guests are going to come and hang out on the boat using man powered water toys, row boats, SUP's, kayaks.
They might stay for the day and sometimes 4 to 6 people might stay overnight on the boat. I will NOT stay on the boat overnight. I will be near by. The boat will not be moved by the guests. The guests will PAY for the time they are on the stationary vessel.

How is this classified and what regulations apply?
Is it a bareboat charter, is 6 pack required?
If a family of 7 rents the boat for the day are there different rules?
If they are all certified members of a private club and the club owns the vessel does anything change?
If they are USCG certified members does anything change?
Is there still a USCG power squadron certification coarse available, my Father did that in the '70s and made me read all the material.

From a LE perspective, if you aren't taking them out on the boat, then it is not a charter, so you do not need a captain's license. If it is just being used as a dwelling/rental then you need to go through your harbor master.

If you DO take them out for a boat ride, since they are paying for it through the rental, it will be considered a charter and you will need at least a 6 pack, with only 6 passengers on it at a time. Somebody good to talk to about it would be the Marine Safety Officer in your area. The nearest Coast Guard Station will be able to point you into the direction of who that is if you give them a call

Thank you, It is a hard one to identify. Also I wonder that if this is a bareboat charter and they are anchored, I am on another boat anchored in the bay, what if I give them ride from the beach in a dingy back to their boat? The ride is not for hire. Is it different in an unregistered 8 foot row boat(no registration fees) than if in a 12 foot RIB with a motor(has CF numbers)?

I am not sure. If they are in any sort of rental agreement with you, and a boat is moving, then a transaction is happening with a boat involved. That is a charter.

You really need to talk to the harbor master and specific MSO in your area. If I personally saw, a Boat, with people on it, going from the beach to another boat, and I was going to board it, and they were in a rental agreement with you for the boat that is anchored, then I am pretty sure we would treat it as a charter, meaning you need a license. If you just get a license then you are covered.

The thing with most charters is that they tell on each other. The guys doing it right don't like illegal charters collecting money because it takes business away from the guys doing it right.

Thank you, I will try to find the MSO for this area.

No worries,

and about the charters telling on eachother, I wasn't implying that you are doing anything wrong, thats just how, and I can only speak for my area, we find out about a lot of the illegal charters around here. For this area, tourism is the main business, so the locals do what they can to keep in intact, and let us know if there is any funny business going on.