Deepwater is a city in Henry County, Missouri, United States. The population was 433 at the 2010 census. Deepwater was laid out in 1…Deepwater is a city in Henry County, Missouri, United States. The population was 433 at the 2010 census. Deepwater was laid out in 1885, taking its name from nearby Deepwater Creek. A post office called Deepwater has been in operation since 1885.