I presume it’s been found when works have been done, now that it has been disturbed it may allow the tide to continue to move it around which could mean an uncontrolled explosion if the detonator fires. Not a good thing at the end of a runway with arriving and departing aircraft. So deal with it now, find if any others are nearby and deal with them also. Once it’s been disturbed is open to elements which could make it go bang!