Which tells me the shrimp are feeding on the cocaine in relatively shallow water, probably near the coast, in an inlet, cove... something with current, but not enough to degrade the bale. 

Plane or boat wreck is possible, but shrimps don’t do well in aviation fuel, oil, and hydraulic fluids. 

Just a hunch, but I’d be betting dollars to donuts that there’s a cocaine haul that got dumped or crashed in that area of the caught shrimp.