Abstract: The invented sea anchor is made from two sheets of flexible material sewn together to create a generally frustum-shaped body. The body is collapsible and has a first end defining a first opening of a predetermined dimension and a second end defining a second opening of a predetermined dimension smaller than the predetermined dimension of the first opening. The anchor includes at least one fin mounted on, projecting outward from, and extending in an axial direction along the frustum-shaped body. The anchor also includes a flexible stiffener encircling a portion of the first opening. The anchor may also include strapping joined to and extending transversely and axially across the frustum-shaped body. The transversely extending strapping may interconnect a plurality of fins.