SAN FRANCISCO — The U.S. Coast Guard planned to end its search at sundown Wednesday for three people still missing after a three-story “pleasure boat” capsized a day earlier in rough waters near Alcatraz Island.

The decision comes more than a day after 20 people were cast into the bay when a wave hit the craft, causing the boat to roll over and sink, said Capt. Jared Toczko, the U.S. Coast Guard’s sector commander for San Francisco. He said there was a “high possibility” that the remaining people unaccounted for remain in the boat at the bottom of the bay, and officials have yet to find the vessel.

Clifford Boisa, 79, of Sutter County was declared dead after being pulled from the San Francisco Bay during a boat outing for a memorial service that turned fatal, according to San Francisco’s Office of the Chief Medical Examiner.

Details of the sinking emerged Wednesday as U.S. Coast Guard crews continued to spread out over the waters of the bay to search for survivors. A dog on the boat also died. Rescue crews — along with a cadre of other private boaters who first hailed emergency crews and personally pulled many of the people from the frigid waters — saved 16 people.

The tragedy happened about 3:35 p.m. The San Francisco Fire Department aid it received a report of a vessel in distress about 600 yards from Alcatraz, Fire Chief Dean Crispen said at a Tuesday news conference.

On Wednesday morning, rescuers continued to use technologies such as thermal imaging, tide prediction and modeling to help direct efforts while spanning out to areas near the San Pablo Bay.

Authorities said their initial belief that the group was on a pontoon boat were not correct. Instead, they later said it was a 49-foot cabin cruiser “pleasure boat” that had three levels. A pontoon boat is considerably smaller and made to be on rivers and lakes.

“Originally, because of the canvas top, it was described as a pontoon boat,” SFFD Lt. Mariano Elias said. He added that the boat was large enough to withstand the waters near Alcatraz.

“The question is whether the boat was designed to be in the bay at that time of day,” he said.

A San Francisco police marine unit arrived first at the scene and found a man in “severe distress,” Crispen said Tuesday. He was hauled out of the water and given CPR, but authorities later pronounced him dead.

Authorities initially believed the vessel — called the Volare, and documented out of Stockton — was carrying 19 people, but the number was later revised to 20 based on witness accounts. Authorities said that there were life jackets on the boat that only some people were wearing.

Three passengers were taken to area hospitals, where they were listed Tuesday in stable condition. The rest escaped injury and were taken to Fort Mason to be reunited with loved ones. They received assistance from the San Francisco Human Services Agency and the American Red Cross.

Crispen said the Volare sank after being hit by a wave or by taking on water.

“This was mostly family members of one another who were on this vessel,” he said.

Initial reports indicated a fire had broken out on the vessel, but authorities later determined witnesses had mistaken steam for smoke, the fire department said in a news release. San Francisco police, the Oakland Fire Department and the U.S. Coast Guard all responded.

Crispen originally said that the boat set sail from the St. Francis Yacht Club, though the organization disputed that on Wednesday. The boat “did not embark from, nor was it associated with” the yacht club, said Susan Ruhne, who is listed as a commodore on the yacht club’s nonprofit filings.

“We share the same bay, and our condolences go out to the family and the friends of the victims of this unfortunate tragedy,” Ruhne said.