Some ships have high voltage dry batteries, like the 300 volt B section of the Navy type 19026 pack battery. They are capable of imparting a very serious, if not fatal, shock to anyone coming in contact with their terminals. When disconnecting them, the current flow should be stopped before disconnecting the plug. It is possible for sufficient gaseous hydrogen to accumulate in this battery to produce a serious explosion if ignited (by the spark caused by pulling the plug while the current is flowing).