It leaves from the adjacent terminal to the cruise ship and includes a brief fireworks display. I've been to P.V. many times and have never done this little cruise.
If you really want a sunset view, I'd take a taxi to Las Carmalitas restaurant on the top of the mountain. It is a real adventure with great food, the best of views high above the bay facing to the west, and a genuine Mexican experience under a palapa at the top of the world. The prices here are very moderate and the restaueant grows their own beef for the excellent steaks.