Private Barnett served in 2nd Lieutenant Able Merander's Coast Guard Detachment between July 14, 1861 and September 5, 1861.

He was mustered into service as a “Seaman” on December 1st, 1861 with Captain Henry Mulrenan’s Florida Volunteer Coast Guards. He remained in this unit until mustered into Confederate service on April 25th, 1862 when was enlisted as a Private in Captain Smith’s Company (Key West Avengers), 7th Regiment Florida Infantry by Major R. B. Thomas at Tampa, Florida for a period of 3 years or the war.

He was present on all rolls until November 3rd, 1862 when he was reported absent sick at Hospital at Knoxville, Tennessee.

He was again reported sick in camp at Knoxville, Tennessee sometime between April 30th and July 13th, 1863; he was present on all rolls until February 20th, 1864 when he was again reported absent in the hospital.

He was transferred to the C.S. Navy on February 24th, 1864. He served in the CSS Savannah for only a few days before before being transferred to CSS Sampson on March 11, 1864. He was wounded in action at Savannah, Georgia during the taking of the USS Water Witch on June 3rd, 1864.

On Tuesday, May 31st, 1864, Lieutenant Thomas Pelot of the Confederate Navy was placed in command of an expedition to capture a US Navy vessel that was at anchor at the mouth of Little Ogeechee River near Savannah. This ship turned out to be the USS Waterwitch.

Some 11 officers and 120 men ended up in the expedition, a number of which were the sailors and marines assigned to CSS Savannah and other vessels of the Savannah River Squadron.

The Union crew of the USS Waterwitch put up a good fight, but they were overwhelmed by the great numbers of southern sailors boarding their ship.

Reports list casualties for the Confederates as nine killed, and fifteen wounded. Private James Barnett was listed as “mortally wounded”; some sources have him being killed outright. Considering that he was married in 1866, drew a Confederate pension, and died in 1886, it would appear that his wounding was somewhat less than “mortal”, and that reports of his death were very much premature.

He survived the war and married Rebecca (Arnold), at Tampa, Florida, on April 26, 1866. He and his wife became the first settlers of what is now Gulfport, Florida, building a house near the shore of Boca Ciega Bay in 1867. Private Barnett died on September 23, 1886; Rebecca applied for and was granted a Confederate Widow's Pension for her husband's service.