I would think for longer run cables, a majority of the run is at a depth, such that anchors don’t even go that deep (except once you get closer to land/shore ) I wonder how far into the seafloor you have to bury a cable such that it’s beyond How deep an anchor can reasonably penetrate (even if the anchor is being dragged). I’m sure this adds quite a bit of cost to the fiber run anywhere you have to bury it, however, I know I’ve seen systems that use a sled and water jets down on the sea floor to bury the cable as it’s run.