The reason why that is a terrible idea is because during WW1, many naval artillery shells used picric acid as an explosive filler, picric acid reacts readily with metals to form highly sensitive picrate salts that are very sensitive to detonation upon being disturbed. Meaning messing with them even slightly has a significant risk of a massive underwater explosion happening. WW1 era military shipwrecks are strictly off limits to divers for that very reason.