The USS Insurgent vanished in August 1800 with 340 men. (Berlitz, Bermuda Triangle, p. 63.)
Alternatively, "In September 1799 the USS Insurgent, a thirty-six-gun French-built warship with 340 crew, vanished." (Quasar, p. 55.)
From the Navy:
Frigate USS Insurgent departed Hampton Roads, VA on 8 Aug. 1800 for West Indies. Never heard from again. Ship and crew of 340 presumed lost in severe West Indies storm on 20 Sep. 1800.