Most of my experience has been in the Boston Harbor, which depending on who you talk to is more dangerous than the hudson, but in my experience most of what they dislike on the hudson is erratic lateral movement. Basically, you're not supposed to meander or transit laterally unless you're a sailboat or a ferry. Police boats / coast guard will approach vessels quickly if it looks like they aren't aware of these rules.

That said, maritime rules are pretty vague. Basically, boats going one direction stay to the right, the opposing direction stays to the left. Situational awareness is important to avoid other slower / faster / larger vessels. "Share the road y'all" is the most succinct way to explain boating in a nutshell haha.