Whale-watching boat smashes into wharf

"Park it anywhere!" a man hollers on the amateur video. The good-natured bystanders along the San Diego Embarcadero chuckle around him.

Seconds later, the small cruise ship blasts its horn five times. The spectators realize the vessel isn't slowing down. It's careening straight toward where they're standing. They panic and scatter. The Adventure Hornblower slams into the concrete seawall.

Here's more on what happened when the ship smashed into the promenade Thursday afternoon:

• Three passengers were taken to area hospitals with "traumatic injuries," according to a tweet from the San Diego Fire-Rescue Department. Four others were treated at the scene and released.

• Why didn't it slow down? Good question. Fire Capt. Joe Amador said crew members told him that the ship's propulsion system malfunctioned, according to CNN affiliate KUSI.

• One passenger told KUSI that he and others clung to the side of the ship because they knew they were going to hit the dock. Another man said he was about 8 inches away from a wall on board, and the impact slammed his head and arms against it. A woman saw a fellow passenger fall and hit her head while skidding across the deck. Amador said none of the injuries was life-threatening, though some people were taken off the ship on stretchers.

• CNN affiliate KFMB reports that Amador said the injuries included back and neck strain, and blood-pressure irregularities. Those who weren't injured had to stay on board the ship at least an hour and a half, until a tugboat could ease the vessel to an undamaged part of the dock.

• Photos posted on social media show damage to both the seawall and the ship. The Coast Guard found that no liquids had leaked into the water, the Port of San Diego said in a statement.

• The 150-foot ship itself is part of the San Diego Hornblower Cruises fleet. The vessel is 22 years old and can carry up to 550 guests, though the Port of San Diego said that only 139 passengers and five crew members were on board during Thursday's collision. The fleet offers daily sightseeing trips around the harbor, including whale and dolphin-watching trips, sea lion viewing expeditions and dinner cruises.

• The older woman -- is she OK? You probably spotted her in the video above, wearing red and carrying a cane. It's impossible not to hold your breath as she moves out of the way just a little too slowly for comfort. You can hear someone on the video saying, "Get that lady out of there!" A young man darts in and appears to help her to safety.

• U.S. Coast Guard Public Information Officer Joel Guzman said a large-scale investigation is being opened.

• San Diego Hornblower Cruises did not immediately respond to a request for comment.

CNN's Amanda Watts contributed to this report.