Who said anything about shrapnel? There's another comment in the thread making the case that "we don't want to just tug harder on the boat, because that might tear a hole in the hull". That could destroy the boat, but... so what?
Because then you'd still have to remove everything, but now you don't have one big, controllable system, but you have lots of pieces that will move in unpredictable ways.
The canal is shallow and narrow, and gravity isn't working in your favor here. A ship has a natural tendency to float (even if it currently isn't). Pieces of debris don't. You will have to remove all pieces that break off, one-by-one.