It sounds from seeing your references you could very well be dealing with pipelines installed in seawater or saltwater, which of course has a S.G. not 1 but a little greater than 1 (e.g. near 1.03).
In any case as to just "float", the sea and incidentally shore and bottom soils or mucks are of course not a stagnant environment (there are different properties, currents and motions etc.), so there could more to consider in stability installation and service etc., than just "float" per Archimedes in fresh water or seawater etc. Like you I will await more learned or detailed comments.