A reel pipelaying vessel of the type having a main pipeline reel (118) mounted for rotation about a horizontal axis, a variable angle pipeline launching ramp (128) having pipeline straightening and tensioning means mounted thereon and having: an improved pipeline launching ramp arrangement including rack and pinion elevator means (140, 142, 144); an improved level winding mechanism for translating the pipeline straightening and tensioning means as the pipe is spooled onto or unspooled from the reel; sea fastening means for restraining axial movement of the reel while the vessel is in transit, thereby increasing the maximum pipeline load for reel bearings (114, 116) of a given load capacity; sponsons (108, 110) for providing additional flotation and strengthening the hull; an improved arrangement of auxiliary reels (120); a cantilever structure (200) for guiding auxiliary lines, providing access to the main reel and protecting the bridge (218) of the vessel; improved pipeline abandonment and recovery arrangements; an improved reel structure; and an improved pipeline clamping arrangement. A method of converting an existing vessel to a reel pipelaying vessel is also described.