Instead of polluting the oceans with these huge cables, we should attach fricken lasers to sharks.
At this point you might think I am going to do another tired re run of the Dr Evil comment, but if you had the imagination that he did you would realise that by also fitting optical detectors on sharks you could have a point to point internet mesh across all sharks in the ocean. SharkNet would not have a single point of failure as like the internet is supposed to do it could find another route in the event of the loss of any shark node.
I humbly submit that Dr Evil was a visionary who was simply ahead of his time and should be canonised into the pantheon of saints alongside Saint Steve of Jobs