HMS Conundrum was the unofficial name given to the large drums used for laying the World War II Normandy landings PLUTO pipeline.
[1] The drums were cone-ended, hence the abbreviation CONUN and were used in the sea, hence subsequent ship HMS Conundrum nickname.
[2] They were 30 feet in diameter and weighed 250 tons.
[2][3][4][5] Views of "HMS Conundrum" components