Many times (USS Texas ex-BB-35 for example) one of the priorities in prepping the ship for permanent display is filling the bilges and bottom tanks with concrete to seal the tanks, fill voids, prevent corrosion, and prevent leaks (or oil or water going places) if somebody twists a valve or a collision/hull plate breaks.
Texas is now re-floated, uses very large sliding rings around vertical pilings to hold her in place, but allow her to float.
They should leave the Intrepid where it is....just tow Manhattan about 1000 miles dues east into the middle of the Atlantic..