A standup paddleboard outrigger includes a long, narrow, lightweight displacement hull and a pair of outrigger pontoons mounted to a bridge. The two parts disengage for easy storage and transport. The hull has a platform to stand on. Paddling with a long handled paddle propels the craft through the water. The outriggers provide lateral stability/support and actuate the rudder in order to make turns. When a person stands on the platform and shifts body weight, the rudder will rotate to the right and the craft will turn to the right. The more weight that is shifted, the greater the turning action. The responsiveness to the shift of body weight can be adjustable for personal preference either firmer or more flexible, as is the turning response of the rudder fine or coarse turning.

A collar assembly for a watercraft includes an elongate tubular casing with a lengthwise sealable opening. A foam core is removably positioned in the tubular casing, and includes a body portion and a plurality of circumferentially spaced foam springs that extend outwardly to engage the tubular casing, to bias the foam core towards a center position in the tubular casing. In some embodiments a body portion of the foam core has a circular cross section, and the foam springs are co-formed with the body portion. In some embodiments the foam core comprises a plurality of longitudinal sections that are enclosed in a membrane having an inflation valve that extends through the tubular casing.

A collar assembly for a watercraft includes an elongate tubular casing with a lengthwise sealable opening. A foam core is removably positioned in the tubular casing, and includes a body portion and a plurality of circumferentially spaced foam springs that extend outwardly to engage the tubular casing, to bias the foam core towards a center position in the tubular casing. In some embodiments a body portion of the foam core has a circular cross section, and the foam springs are co-formed with the body portion. In some embodiments the foam core comprises a plurality of longitudinal sections that are enclosed in a membrane having an inflation valve that extends through the tubular casing.

An internal canoe frame acts as a mount for retractable outriggers, foldable panels, and pontoons. With the outriggers, panels, and pontoons, the canoe can be adapted to provide a stable multi-purpose waterborne platform. In some embodiments, the platform may also include a support frame for a tent, to provide a waterborne camping site for an intrepid canoer.

An inundation prevention system for ship is provided. The inundation prevention system for ship includes a fire-extinction gas ejection part configured to eject a fire extinction gas to an installation area prepared in a hull, an airbag part of 3D shape disposed in the installation area, and an airbag actuation part configured to supply the fire extinction gas to the airbag part, if inundation occurs in the installation are, and to inflate the airbag in the installation for compulsory buoyancy.

An inundation prevention system for ship is provided. The inundation prevention system for ship includes a fire-extinction gas ejection part configured to eject a fire extinction gas to an installation area prepared in a hull, an airbag part of 3D shape disposed in the installation area, and an airbag actuation part configured to supply the fire extinction gas to the airbag part, if inundation occurs in the installation are, and to inflate the airbag in the installation for compulsory buoyancy.

A sponson attachment for an airboat allows the airboat to increase its safety and stability very quickly. A method for attaching a sponson to an airboat hull includes attaching first and second flexible tethers to a side of the sponson. The method also includes removably securing the first flexible tether to an exterior of the airboat hull adjacent a gunnel, and removably securing the second flexible tether below the first flexible tether on the exterior of the hull.

A collar assembly for a watercraft includes an elongate tubular casing with a lengthwise sealable opening. A foam core is removably positioned in the tubular casing, and includes a body portion and a plurality of circumferentially spaced foam springs that extend outwardly to engage the tubular casing, to bias the foam core towards a center position in the tubular casing. In some embodiments a body portion of the foam core has a circular cross section, and the foam springs are co-formed with the body portion. In some embodiments the foam core comprises a plurality of longitudinal sections that are enclosed in a membrane having an inflation valve that extends through the tubular casing.

A collar assembly for a watercraft includes an elongate tubular casing with a lengthwise sealable opening. A foam core is removably positioned in the tubular casing, and includes a body portion and a plurality of circumferentially spaced foam springs that extend outwardly to engage the tubular casing, to bias the foam core towards a center position in the tubular casing. In some embodiments a body portion of the foam core has a circular cross section, and the foam springs are co-formed with the body portion. In some embodiments the foam core comprises a plurality of longitudinal sections that are enclosed in a membrane having an inflation valve that extends through the tubular casing.

A variety of multi-use, configurable watercraft is disclosed. A first type of watercraft used in a first water-based activity may be used as a component in a second type of watercraft used in a second water-based activity. For example, a stand-up paddleboard (SUP) may be used for paddle boarding, and then converted into a kayak, sailboat, catamaran, motorboat, or other type of vessel by adding one or more components to the SUP. In one embodiment, two paddleboards are used to construct a variety of multi-hull watercraft.