Newport Beach Harbor looked more like a bumper boat's course after one man allegedly stole and crashed a multi-million-dollar yacht into other boats ... prompting a police response.
Check out the insane video, you see the man attempt to reverse, and then go forward in full speed -- wrecking into other vessels -- including a sailboat that totally loses its mast in the collision.
Law enforcement sources tell TMZ they got a call just after 10 AM Thursday morning for a "possible stolen vessel."
An eyewitness tells us a police boat eventually arrived on scene and got the boat stopped.
We don't yet know who the alleged thief is, or what his plan was in taking the boat.
Story developing ...