The term 'clumsy vessels' can refer to two different types of ships: ARKS and hulks. An ark is a large, open-decked vessel used for carrying cargo or passengers, typically powered by sails or oars. Hulks are large, slow-moving ships that were once used as prison ships, but are now mainly used for storage or as floating museums. Both types of ships are considered clumsy vessels due to their large size and slow speed.