Deep ocean water (DOW) is cold, salty water occupying about 90% of the volume of the Earth’s oceans. DOW has a very low temperature, typically from 0 to 3°C, and salinity of about 3.5%(35psu). These properties provide an energy gradient and distinguishing water quality; hence, skillful application of science and engineering can harness the energy and quality for productive uses such as air conditioning. desalination, drinking water, crop irrigation, and ocean thermal energy conversion. Consequently, upwelling and transporting mechanisms have been issued for the massive production and the design, manufacturing, and installation of the subsea risers have been investigated for specific and applications. this study presents one of the investigations which focus on structural responses of subsea risers in water flows. Narrowing but not limiting the subject, various structural members(so-called couplers) making connected-risers are intentionally devised and numerically tested in water flows, using associated general purpose numerical programs. In the process, water fields were constructed with an inlet, outlet, smooth wall, and symmetric boundary conditions and then flow environments and structural responses were subsequently identified. Accordingly the flow environments and structural performances are evaluated in terms of drag coefficients, pressure fields, environments and structural performances are evaluated in terms of drag coefficients, pressure fields, displacements, and equivalent stresses. Finally the principal characteristics (dimensions of structural couplers and shapes) controlling the environments and performances were recognized in the future design practice. It is known that the stability of subsea risers is significant when the risers transport deep ocean water to lands. In marine environment, it is hard to predict or estimate external forces on the risers. Also, the damage occurred by external forces can be severely extended into structural instability; hence, the structural design should be carefully carried out. Especially, the structural members connecting pipes are critically weak against external forces so that in the study we investigated the structural responses of the connecting members in water flows. For the purpose, 3D finite element models were constructed by introducing a connecting method, which adopted adhesive epoxy. And to analyze a flow space, a cube filled with water was formed Finally, considering various water flows the displacements and stresses were obtained and compared.