who invented the first submarine used in war
History of submarines The submarine became a potentially viable weapon with the development of the first practical self-propelled torpedoes. The Whitehead torpedo was the first such weapon, and was designed in 1866 by British engineer Robert Whitehead. His 'mine ship' was an 11-foot long, 14-inch diameter torpedo propelled by compressed air and carried an explosive warhead. The device had a speed of 7 knots (13 km/h) and could hit a target 700 yards (640 m) away.[27] Many naval services procured the Whitehead torpedo during the 1870s and it first proved itself in combat during the Russo-Turkish War when, on January 16, 1878, the Turkish ship Intibah was sunk by Russian torpedo boats carrying Whiteheads.
Mariana Trench Four descents have been achieved. The first was the manned descent by Swiss-designed, Italian-built, United States Navy-owned bathyscaphe Trieste which reached the bottom at 1:06 pm on 23 January 1960, with Don Walsh and Jacques Piccard on board.[13][22] Iron shot was used for ballast, with gasoline for buoyancy.[13] The onboard systems indicated a depth of 11,521 m (37,799 ft), but this was later revised to 10,916 m (35,814 ft).[23] The depth was estimated from a conversion of pressure measured and calculations based on the water density from sea surface to seabed.[22]