Abstract: Systems and methods to provide a watercraft fin box with a retractable fin. The fin box may be fitted to a watercraft such as an inflatable paddle board. The retractable fin is associated with a lever that allows the retractable fin to rotate within a body of the fin box. An elastic member positioned within the body of the fin box operates to urge the retractable fin away from the body when the retractable fin rotates into the body. The elastic member does not urge the retractable fin away from the body when the fin box is fitted to a watercraft and the retractable fin of the fin box is positioned to face the Earth, such as when the watercraft is placed atop water with the retractable fin immersed in water.

Abstract: Systems and methods to provide an exterior stringer system inflatable paddleboard. The exterior stringer system inflatable paddleboard maintains the benefits of a baseline inflatable paddleboard while providing increased strength, such as increased rigidity or stiffness. The exterior stringer system is positioned on the bottom surface of a baseline inflatable paddleboard. In one embodiment, the exterior stringer system is formed by a set of longitudinal stringers positioned on opposite sides of an inflatable paddleboard and a set of transverse stringers arranged in an X configuration between the longitudinal stringers.

Abstract: Systems and methods to provide an exterior stringer system inflatable paddleboard. The exterior stringer system inflatable paddleboard maintains the benefits of a baseline inflatable paddleboard while providing increased strength, such as increased rigidity or stiffness. The exterior stringer system is positioned on the bottom surface of a baseline inflatable paddleboard. In one embodiment, the exterior stringer system is formed by a set of longitudinal stringers positioned on opposite sides of an inflatable paddleboard and a set of transverse stringers arranged in an X configuration between the longitudinal stringers.