One of the victims of last years Tsunami that hit Japan was a steel fishing boat, the Ryou-Un Maru.  This ship had been set adrift and has been slowly crossing the Pacific till it got within range of the world's shipping lanes.  The US Coast Guard had been tasked to do something about it, so of course they thought sinking it would be the best idea, although you would think someone owned that boat.  Not being claimed was the end for that ship and the coast guard, armed with a 25mm Bushmaster chain gun and an automatic grenade launcher, set about to make mincemeat out of it.  Well at least that was the plan, but many 25mm rounds later the ship was smouldering but refused to sink.  Finally after many rounds from the Mk. 19 grenade launcher, the ship finally acquiesced and sank beneath the waves.

Mk 19 in action

One of the requisites for winning WW2 against the Japanese empire was the necessity of sinking every floating Japanese thing they had.  If their ships had been as stubborn as the Ryou-Un Maru, the war would still be far from over.

Ryou-Un Maru