Context: CREATE TABLE table_name_21 (ship_types_delivered VARCHAR, total_vessels_built_for_usmc VARCHAR)
Question: what is the ship types delivered when the total vessels built for usmc is 13 ships for usmc (plus 37 more for usn)?
Answer: SELECT ship_types_delivered FROM table_name_21 WHERE total_vessels_built_for_usmc = "13 ships for usmc (plus 37 more for usn)"