A device for restraining a swimmer in a variety of settings including a post, tie portion, tether assembly, and restraining belt coupled to the tether assembly and swimmer. An anchor assembly provides an anchoring collar fixed at one end and in sliding engagement with the post at another end. In operation, a swimmer applies a variable tension from the restraining belt across the tether assembly to the tie portion of the post. In sliding engagement with the post, the anchoring collar provides a tensile force to the post to counteract the swimmer's variable tension and to maintain the post both in a longitudinal position within the body of water and in continuous contact with the underwater floor. The device may include a base assembly that is releasably coupled to the post and enables the post to pivot in the direction of the tensile force applied by the tethered swimmer.