Four sailors escaped serious injuries after their sailboat was slammed into the Redondo Beach Pier by wind-driven waves, to the amazement of witnesses on Thursday.

High onshore winds pushed the sailboat closer and closer to the pier, multiple witness videos of the 7 p.m. crash showed. A large wave finally overturned the vessel, dumping the four occupants into the choppy waters of King Harbor.

"A wave came ... it broadsided them, it threw all the people out. ... If it weren't for the pier, they would have been hurt badly because the next wave took the boat into the pier and smashed it in half," said witness Tommy Smith. "The lifeguards were right on them, pretty quick. The guys were so lucky, it was unbelievable."

The boat slammed against the pilings and righted itself but eventually broke apart.

Employees at Tony's on the Pier, a restaurant with a close view of the harbor, saw the crash quickly unfold through windows onto the water.

"The current was pretty intense because they couldn't get out of the water," said worker Alejandro Ruiz. "The boat hit the pillars a couple of times and it cracked in half and it sunk. ... I've never seen anything like that."

Authorities said they expected to recover the wreckage.

All four people were rescued after Los Angeles County lifeguards, Harbor Patrol and Redondo Beach firefighters responded.

The condition of the four rescued boaters on Friday was not clear, but their injuries had not been serious.

Smith, a bartender at Tony's on the Pier, said he thought the wind speed had risen from 12 to 15 knots when the boaters went out to about 25 to 30 knots when they crashed.

"I was shocked that nobody got hurt," he said.