TRAILERING SUPPORT DEVICE AND METHOD, AND MARINE VESSEL INCLUDING TRAILERING SUPPORT DEVICE

A trailering support device capable of facilitating trailering for loading of a hull onto a trailer. The trailering support device performs automatic vessel steering control so as to move the hull toward the trailer, estimates, based on a content of the automatic vessel steering control, a position and an azimuth of the hull at a predetermined timing after start of the automatic vessel steering control, detects the position, a steering angle and the azimuth, of the hull, respectively compares the position and the azimuth estimated with the position and the azimuth detected at the predetermined timing, and determines, based on a comparison result, whether the loading of the hull onto the trailer is performable, and in a case where it is determined that the loading of the hull onto the trailer is not performable, notifies of that matter.