forcing your way onto a vessel is piracy... hell, even the coast guard or sheriff has to ask your permission to board your vessel....(if you did not ask for and receive permission to board, you have forced your way aboard)
In Jacksonville Florida the JSO likes to perform "shakedowns" on people living aboard boats in marinas and visiting cruisers at anchor. First, they come hammering on your boat early in the morning, and you are greeted by a half dozen officers armed for bear, who ask permission to board, and if you ask to see a search warrant, will tell you they are there to inspect your marine toilet to be sure it does not flush overboard. If you allow them aboard, they search your boat from stem to stern for contraband. If you deny them permission to board and demand a search warrant, you are immediately arrested. The charge: resisting arrest. They did it to me, I've seen them with my own eyes do it to others. In court the judge threw my charges out because he was so familiar with the tactic, his own words were "you were guilty of saying 'no' to the JSO".
In addition, many times when they hammer on a person's boat and there is no response, they go aboard and try the hatches and storage compartments, and if any are unlocked, they go through the contents for a quick look. This is blatantly illegal. At one marina a resident caught this on his cellphone, he was arrested and his cellphone mysteriously ended up in the deep six.
A friend of mine was taking his rather huge motor vessel to an inexpensive marina in Jacksonville that allowed people to work on their boats...I knew the area and that it was one of the favorite places for the JSO to get their kicks rousting boat people, but my friend was a legal scholar, and when he heard my horror story, he kept saying "but they can't do that." I told him "that's not the point, they will do that."
"But they can't."
"But they will."
Six JSO asked for permission to board. He refused permission. They arrested him, dragged him to a sheriffs car in cuffs, searched his boat in his absence sans warrant, and when he bonded out, he was still saying "but they can't do that."
"But they did."
"But they can't."
"But they did!"