Witnesses caught the crash on camera.
There are holes in the metal hull and it struck hard enough to break the concrete and metal railing on the dock.
People on the dock and aboard the boat could tell something was wrong based on how fast the ferry approached. Witnesses pulled out cell phones and recorded.
"The captain-- there was nothing over the intercom and you would think that they would have honked a horn or anything to give people a heads up," said Jack Wahl, a ferry passenger.
Passengers on Golden Gate Ferry's MS San Francisco say they had no official warning of the impending crash.
"We were joking about we're going way too fast to be coming into this and immediately after we stopped joking about it, we smashed into the first piling and we deflect into the actual port itself," said Gavin Martz, another ferry passenger.
People eating at the San Francisco Ferry Building saw the boat coming their way around 2:30 p.m.
"I did yell to my table, 'Oh my gosh, here comes a boat and he's coming in hot,'" said Kelly Schirber, a witness who dined at The Slanted Door.
"It was definitely very hectic. There was quite a bit of yelling going on board," recalled Martz.
Some took out cameras as the ferry approached, while others ran.
"I thought it was going to go straight into the restaurant, so I started running the opposite direction," said Angelina Sivoia, who was dining with her mom, Kelly Schirber.
The impact cracked the concrete, knocked over the railing, and shook The Slanted Door restaurant.
"The handrail looks like a simple piece of metal. It's actually a deceptively strong safeguard to make sure that if something like this were to happen, there would be no further damage to people on land," said Priya Clemens, a Golden Gate Ferry spokesperson.
US Coast Guard investigators will now look into the computer systems to determine how fast the boat was traveling and if the captain was in control.
"The captain said it was technical failure," said Wahl.
All five crew members will be drug tested and interviewed, which is policy, according to Golden Gate Ferry. The Coast Guard will also review the boat's maintenance records.
"The vessels are inspected frequently by the US Coast Guard, so there is a lot of oversight," said Lt. Commander Matthew Zinn, US Coast Guard SF Investigating Officer.
The boat can carry some 750 passengers, but had a light load of 53 people Friday. Two people reported minor injuries. A concession worker had a bruised hip and a passenger complained of a sore back, but refused treatment. Ferry service was not delayed due to the crash. It will go on as scheduled, but without the MS San Francisco during the investigation and repairs.