I have no experience in this, but although this fact and that the technical data are somewhat scarse:
I'm gussing that the pure mechanical conditions must alter when the barge rises. Either more or less of the hose submerged (hose updrift up from water - and yes, I'm aware that the vessel is riding at eqaul dept at all times, if it doesn't sit at bottom for the low tide ;-) ) or hose more or less resting on bottom (support of pipelengthlength from seabed) combined with altered/unfavourable angles resulting from fixed lenght of pipeline and fixed endpoints as barge alters position.
I've seen intake lines supported by outreaching booms, lines hung up with slacks (loops) to give better balance at altered length. An idea to look into this perhaps?