This paper deals with the motion of a submerged tethered system subject to large deformations and displacements. A tethered system usually employs a cable or wire rope to tether an attached piece of equipment to the ground or to a vehicle, e.g., a remotely operated vehicle (ROV) in the sea. The motion of a tether was modeled using the Absolute Nodal Coordinate Formulation in which absolute slope of elements are defined as nodal coordinates. Herein, this formulation is adapted to account for hydrodynamic drag, buoyancy and added mass. By using the slope coordinates, the hydrodynamic drag acting on the curved shape of the deformed elements can be accurately calculated. Three kinds of experiment were conducted into the fundamental motion of the submerged tether when subject to large deformations and displacements. The numerical results from the proposed model agreed well with the experimental results.