The name Horse Marines was given to a volunteer ranger group of 1836. Anticipating that Mexican troops might land on the Texas seaboard, Gen. Thomas J. Rusk detailed mounted ranger companies to patrol the coast. On May 29, 1836, Maj. Isaac Watts Burton with about thirty men was ordered to scour the sector between the mouth of the Guadalupe and Mission Bay. Walter Lambert, Nicholas Lambert, and John Keating, Refugio colonists who were with the army and knew the country, accompanied the rangers as guides.
On June 2 Burton learned of a suspicious vessel in Copano Bay and hurried his force to that point. By daylight next morning he had his men in ambush near Copano. Two or three rangers made signals of distress. The vessel hoisted both American signals and Texan colors, but these were not answered; they then hoisted Mexican signals, which the men answered as distressed Mexicans. The captain and four sailors, who came in a boat to their assistance, were immediately seized, and sixteen of the rangers took their places in the boat and rowed out to the vessel, the schooner Watchman, loaded with provisions for the Mexican armies. The crew, mistaking the rangers for their comrades, permitted them to come aboard without resistance. One account states that Col. Juan Davis Bradburn, a passenger aboard the vessel, perceived the situation, jumped into a small boat, and rowed away safely.
Burton prepared to send the Watchman to Velasco as a prize of war, but unfavorable winds delayed immediate departure. The vessel lay in the harbor until June 17, when two more vessels were sighted off the bar. These schooners, the Comanche and the Fanny Butler, were also loaded with supplies for the Mexican army. The captain of the Watchman was required to decoy the captains of the Comanche and Fanny Butler aboard the Watchman. The officers were seized, and their ships and cargoes fell into the hands of the rangers without struggle.
The three prizes were first taken to Velasco and then sent to Galveston, where the cargoes were condemned, but the vessels, being American owned, were eventually returned to their owners. Col. Edward J. Wilson of Lexington, Kentucky, wrote of the capture of three Mexican vessels by a troop on horses and said that he supposed they would be called "Horse Marines."