As a contribution to the new field of WaterHCI (Water-Human-Computer Interfaces), we proposed and developed a smart SUP (Stand-Up Paddleboard) to assist a person with a disability (shoulder + back injury) to continue paddling and cross-country swimming (pulling a paddleboard to carry cargo while swimming). The paddleboard technology consists of two thrusters (motorized propellers) driven (1) in proportion to the flex of a paddle, to maintain the same feeling as normal paddling but with easement on shoulder strain, or (2) in proportion to the tension of a tow line attached to a waist strap around a swimmer’s waist. We also propose a controller for controlling a throttle using paddle flex or the tension of a pull cord. We also propose the use of our throttle control technology in transporting the paddleboard by way of a pulled wagon or an electric cargo bicycle (loaded up with the paddleboard and related supplies), at times when it is necessary to push it up steep hill. The wagon has a pull cord similar to the paddleboard, and the bicycle consists of a handlebar equipped with force sensors to provide the similar effect to pulling the paddleboard or wagon.