These latter two craft are shaped like a tear drop for minimum resistance in the water, and have an underwater velocity of 20 knots (twenty nautical miles per hour). They operate to a depth of over 200 meters, can last at sea for two months without taking on fuel or supplies and have a range of over 10,000 nautical miles.
水面下的航速約廿節（每小時廿海浬）、能進入超過二百公尺的深海層，且可在海中持續航行兩個月，不需泊岸補充油料，航程達萬浬以上。