I think the best thing to do about those sunken chest is to randomize the locations they spawn at.
It was a huge over site by XL to spawn these chests in static locations. They essentially catered to the bots and hackers who could teleport to the coordinates of the chests.
If the staff can do anything to these, I implore them to make the sunken ship locations random. These static chests convert a fun treasure hunting excursion into a grind for the sub design and scroll components, as we repeatedly return to the exact same locations....over and over again.