Abstract: Apparatus includes an offshore platform riser subtended by a joint chamber having port means for receiving a subsea pipeline and access means for a submersible capsule. The riser and chamber are attached to the platform in such manner as to provide for thermal expansion and to permit detachment when an abnormal loading is encountered. Platform winch means attached to cable means passing through the riser and chamber are used to pull an end of the pipeline into the chamber. Personnel utilizing the capsule then enter the chamber for completing the joining of the pipeline and riser. The joining and subsequent inspection operations are conducted at substantially atmospheric conditions in the chamber.