Yes you pretty much have it. A picture is worth a thousand words here:
The reason I asked is that your situation was such that it looked like it might have been possible to apply. I have used this in swiftwater rescue training where boats were deliberately pinned by instructors and then the students were required to unpin them. But I have never had a real life situation in which I could use it.
The technique requires the rescuer to approach the boat in a stable and safe manner, usually from a downstream direction, and also requires the rope to be floated or passed beneath the pinned hull, two requirements that often don't apply. But congratulations for knowing it and being able to apply it here.
