Abstract: Apparatus for laying large pipe sections underwater without on-site manual participation. A beam is releasably attached to a pipe section that is to be lowered to the floor of the water body and attached to the open end of the previously laid pipe section. A positioning fork depending from the beam is settled onto the prior pipe section with the fork legs straddling the pipe and assuring alignment of the pipe ends. Positioning rams in cooperation with landing gears on the fork legs achieve concentric abutment of the end flanges. The flange on the new pipe section is rotatable and a positioner from the beam is releasably attached to the rotatable flange and rotated therby to align bolt holes through the flanges. A wrench carried on a rigging releasably attached to the new pipe section behind the flange is movable between the bolt holes and pushes bolts partially pre-inserted in the bolt holes through the flanges and into engagement with nuts pre-positioned behind the bolt holes of the fixed flange.