To provide a connecting device of a vessel remarkably improving stability and maneuverability in low speed navigation.

A device and a method to increase low speed maneuverability and stability of a marine navigation vessel 10 are disclosed. The device is furnished with a link device to connect a secondary steering vessel 12 or a partial hull to a primary vessel 10 or a partial hull so that the secondary steering vessel 12 or the partial hull rocks its head against the primary vessel 10. As a favourable embodiment, the link device has a pair of link devices on which one link arm 16 is pivotally connected to the primary vessel 10 and the secondary vessel 12 on boty sides of the secondary vessel. The device also has a device to actuate and control head-rocking motion of the control vessel or an auxiliary vessel.