There's a lot of things that can happen I suppose when you've got 200 plus yards of line out for long periods
I agree i love to dive all my spots. I find it funny how all the hot spots for shark fishing have some kind of baggage to them kinda like single women.
lmao haha only you calab 
, this is a good topic that i hope every sharker over looks once twice and some!!
I have been suffering from more cutoffs than ever before. Line doesn't seem to matter. Hi-vis yellow PP, white JB hollow and clear 100# mono. Usually pretty obvious when it is Bluefish or Spanish as the cuts are 1" apart. Had them around for several weeks then started getting larger abrasions and cuts to the line. Seem to be small sharks. But I had a hard time believing the chances of a shark actually bumping into the line with its teeth were that great. Eventually I realized most of the cutoffs were at the same distance which correlated with the sandbar. Started reeling in when I got just a "bump" (without the line going completely slack) and often discovered teeth marks 4"+ wide. Pretty frustrating when you lose 2-4 a weekend. Fortunately, many of the high vis yellow PP was recovered on consecutive trips as it floats to the surface. Got a couple of double uni-knots in the PP now. 
This is the worst when it happens and sometimes there just isn't much you can do about it. As previously stated the culprits are most likely bluefish, smacks, sandbar sharks, sandbars, coral, or anything else abbrasive, wether it's an old wreck or a crab trap.
I fish the Cape San Blas area and I've been cut more times than I can count. I'm almost certain that it's the bluefish attacking my line.