Authorities said a man and woman were inside a mini van headed west on County Line Rd. toward Caney Creek when they lost control on a curve. The driver overcorrected and hit a guardrail, then the van left the road.
The vehicle flew about eight feet off the roadway, then fell about 30 feet into the creek.
Emergency personnel had difficulty getting to the victims, officials said. A North Montgomery Country Fire Department ladder truck was used to get them out of the submerged van.
Officials said the male driver was taken to an area hospital in critical condition. The female passenger died at the scene.
According to investigators, it appeared the man was wearing a seatbelt, but the woman was not.
The crash remains under investigation.