Low Tide Salvage

Ack Mercer has been diving the Gulf Coast for fifteen years. He knows the feel of the water - the way the current runs, the temperature gradients, the particular quality of visibility at different depths and different seasons. He's gone down on a lot of wrecks. Nothing that's ever changed anything. The survey job is routine: a marine archaeology firm out of Savannah pays five hundred dollars for a wreck survey, mapping the site, documenting the hull, staying outside the structure.
The coordinates are six miles offshore. The weather window is closing. Jack needs the work. He finds the wreck in forty-eight feet of water - a massive cargo vessel, prewar construction, buried to the turn of the bilge in accumulated silt. He photographs the hull, notes the collapse in the midship section, documents the scattered debris. He's almost finished when his light catches something in the shadow of a displaced hull plate. What he finds is not supposed to be there.