The missing boaters were on board the 20-foot vessel along with three others when it began taking on water Friday evening, according to the Galveston Fire Department.
Good Samaritans rescued the three survivors who were found swimming toward the causeway, Battalion Chief Tim Johnson said.
The two missing were believed to be a 26-year-old and a 46-year-old man.
The three rescued were wearing life jackets, Johnson said.
It wasn't clear what caused the boat to take on water, but waves were one to two feet and winds were gusting to 20 mph at the time.
Galveston Beach Patrol, the Galveston Fire Department and the U.S. Coast Guard were among the agencies who were continuing to search Saturday for the missing men.
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