The Peralta, carrying 4,000 passengers, approached the Oakland ferry terminal, and as passengers gathered at the docking end, the bow sank into the water. Waves swept over the deck. Passengers jumped overboard or were swept into the water.
In part, panicking passengers caused the accident. But the main cause was failure of the trimming tanks, tanks designed to be filled with water to counterbalance the weight of passengers. The tanks should have been filled in the aft when commuters congregated on the bow, but on this occasion the wrong tanks were filled, plunging the vessel headfirst into icy waters. The tanks were never used again.