Abstract: A seat assembly for use on a stand-up paddleboard includes a base member which defines a base axis. A support shaft, with an affixed seat member, is engaged with the base member. In detail, the support shaft defines a shaft axis and is formed with diametrically opposed slots along the length of the support shaft. Protrusions, formed on the base member, are engaged with respective slots on the support shaft to selectively move the support shaft on the base member between a stowed configuration wherein the shaft axis is substantially perpendicular to the base axis, and a sitting configuration wherein the shaft axis is coaxially aligned with the base axis. In operation, a reconfiguration of the seat assembly is accomplished to provide the stand-up paddleboard user with a place to sit during an on-the-water operation of the stand-up paddleboard.