Editing SEAL Delivery Vehicle (section)

===Mark 9 SDV===
Despite being a development of the Mark 8 SDV, the Mark 9 is a very different vehicle, designed for attacking surface ships rather than deploying SEAL teams on clandestine operations. Indeed, the Mark 9 and Mark 8 share very few common parts.<ref name=Klose /> The Mark 9 carries two SEALs, a pilot and a navigator, and two [[Mark 31 torpedo|Mark 31]] or [[Mark 37 torpedo]]es for standoff attacks against ships.<ref name=Williams>{{Cite book| publisher = Naval Institute Press| isbn = 9781612510064| last = Williams| first = Gary| title = SEAL of Honor: Operation Red Wings and the Life of LT. Michael P. Murphy (USN)| date = 2010-12-07| url=https://books.google.com/books?id=e8DnFCKgxzYC&pg=PA101| page=101}}</ref> These torpedoes can travel up to {{convert|3|nmi|km}} in a straight line,<ref name=Kelly98 /> carry a {{convert|330|lb|kg|adj=on}} warhead, and are capable of sinking ships as large as [[cruisers]].<ref name=Sutton>{{cite web |last1=Sutton |first1=H.I. |title=SDV Mk9: US Navy SEAL's torpedo armed mini-sub |url=http://www.hisutton.com/SDV%20Mk9.html |website=Covert Shores |access-date=20 September 2018 |date=21 August 2016}}</ref> In addition to torpedoes, the Mark 9 also carried [[limpet mine]]s and satchel charges in a large cargo compartment aft of the pilot and co-pilot.<ref name=Museum />

The Mark 9 is designed to clandestinely approach enemy vessels while submerged, surface to fire torpedoes, and then escape unnoticed. As such, its design incorporates [[Stealth technology|stealth]] characteristics, including a lower profile and sonar absorbing materials.<ref name=WalshWalker>{{Cite book| publisher = Simon and Schuster| isbn = 9780671868536| last1 = Walsh| first1 = Michael J.| last2 = Walker| first2 = Greg| title = SEAL!: From Vietnam's PHOENIX Program to Central America's Drug Wars : Twenty-six Years with a Special Operations Warrior| date = 1994| url=https://books.google.com/books?id=gMgxIvUz104C&pg=PA43}}</ref> The Mark 9 SDV was intended to attack ships in shallow coastal waters that full-size submarines could not enter,<ref name=Museum /> and to draw attention of an enemy fleet away from the Mark 9's parent submarine.<ref name=Sutton /> Though it proved very effective in exercises, the Mark 9 was retired starting in 1989 and was fully phased out of service by the mid-1990s due to manpower and budget constraints and because all of its capabilities save launching torpedoes were duplicated by the Mark 8.<ref name=Museum />

The pilot and navigator operate the vehicle from a prone position and lay side by side. The prone position gave the Mark 9 a low profile and enabled it to operate in very shallow water,<ref name=Kelly>{{Cite book| publisher = Open Road Media| isbn = 9781504047456| last = Kelly| first = Orr| title = Special Ops: Four Accounts of the Military's Elite Forces| date = 8 August 2017| url=https://books.google.com/books?id=rTotDwAAQBAJ&pg=PT123}}</ref> although SEALs reported that staying prone for the entire duration of an operation was uncomfortable.<ref name=Sutton />

The Mark 9's sleek profile and independent [[diving planes]] enabled it to be especially agile.<ref name=Sutton /> It was also faster than the Mark 8, reaching speeds of {{convert|7|-|9|kn|kph}}, owing to its twin [[screw propeller]]s and high-performance [[silver-zinc batteries]].<ref name=Museum /> Its speed and agility led operators to compare it to flying a fighter jet or driving a sports car.<ref name=Kelly />

[[File:US Navy 060206-N-1464F-003 A SEAL Delivery Vehicle (SDV) is loaded aboard the Los Angeles-class fast attack submarine USS Dallas (SSN 700) in preparation for a Special Warfare Training exercise.jpg|thumb|A Mark 8 SDV is loaded aboard ''Los Angeles''-class submarine {{USS|Dallas|SSN-700|6}}]]