The boat was competing in the 40th annual Regata de Amigos. The race, which covers 610 nautical miles from Galveston to Veracruz, Mexico, started Friday and continues into next week.
The crew included four college students and two safety officers, Texas A&M at Galveston said in a news release.
Three of the students - Steven Guy, Joe Savana and Travis Wright - attend Texas A&M at Galveston, the school said in a news release. The fourth, Ross James Buzbee, attends Texas A&M in College Station, the school said.
The safety officers are Steve Conway of Texas A&M at Galveston and Roger Stone, a Galveston resident, the school said.
Coast Guard officials said the keel of the overturned vessel was ripped off, indicating the sailboat may have hit something in the water, according to the school. Race director Kevin Box said the loss of the keel can cause a boat to overturn in seconds.
Petty Officer Renee C. Aiello said a floatation device was found near the boat.
The boat went missing 11 miles south of Matagorda, which is about 110 miles down the coast from Galveston.
The school said the Coast Guard will continue searching throughout the night.