A process for installing or removing a subsea structure in a non-vertical manner at a well includes securing a plurality of barges together in a linear formation in which one of the plurality of barges has a downline extending therefrom, connecting an end of the barges to a primary vessel, moving the primary vessel such that one of the barges is positioned over a target at or adjacent to the well, connecting a plurality of secondary vessels by plurality of mooring lines to an opposite end of the barges, tensioning the mooring line so as to fix the opposite end of the barges, positioning a deployment vessel away from the barges, deploying an ROV, manipulating the ROV so as to connect the subsea structure to the downline, and moving the downline and the subsea structure toward or away from the well.