Worldwide, there are more than 81,600 missing U.S. military personnel, including:
72,350 from World War II,
7,550 from the Korean War
1,584 from the Vietnam War
Over 41,000 of the total are presumed lost at sea............
Silent service losses, plus surface navy losses, account for about half of the WWII total, if memory serves. The Tomb of the Unknowns got its start after WWI if memory serves, because the remains were so mauled by the weapons of that time, and a lot of soldiers were blown to bits leaving no identifiable remains.