SELECT TYPE FROM ship GROUP BY TYPE ORDER BY COUNT(*) DESC LIMIT 1
Please show the most common type of ships.
[Schema (values) (types)]: | ship_mission |  mission : mission_id (text) , ship_id (number) , code (number) , launched_year (text) , location (number) , speed_knots (text) , fate (number) | ship : ship_id (text) , name (number) , type (number) , nationality (text) , tonnage (number);