In this paper, the finite element method is employed for the purpose of studying a general utility technique for calculating static and dynamic response of general three dimensional underwater Line Structures. Here, the structures composed primarily of long, flexible suspension members are called Line Structures, e. q. cables, drill strings etc. Transverse stiffness of Line Structures is secured mainly by tensile forces. Underwater line structures have three combined nonlinearities, i. e. structural, hydrodynamic and material. Consequently a general approach for calculating their highly complex behavior is limited to one of numerical methods. In this calculating program, bending stiffness is included for the purpose of the ability to calculating the behavior of frame structures in the ocean as well as underwater line structures as defined here. Numerical results obtained by this approach about three relatively simple problems, i. e. towing, free fall anchoring and laying pipeline, are shown and discussed. Then, this numerical approach is seen general and useful for calculating the static and transient response of general underwater line structures.