Abstract: A marine vessel comprises at least one hull stabilized by at least one pair of outboard sponsons and propelled by propulsion means carried by the sponsons or hull. One aspect of the invention is shown in FIG. 7, where a marine vessel (20) is provided with first second pairs of outboard sponsons (230, 231), with the first pair (230) disposed forwardly of the second pair (231). The sponsons (230) of the first pair are disposed at a higher level than the sponsons (231) of the second pair. At the load water line (208) of the vessel, the sponsons (231) of the second pair are in contact with the water while the sponsons (230) of the first pair are disposed above the waterline (208). As shown in FIG. 12, should the vessel (201) heel to one side, the sponson (230) of the first pair on the heeling side of the vessel is brought into contact with the water, so as to create an upwardly acting restoring force (250) which tends to stabilize the vessel. Other aspects of the invention are disclosed.