The Ghost Girl is proven to exist in Ocean Beach. It is based on the female pedestrian models around the beach, when the player drives them on his motorcycle, into the shallow water, they vanish. Players have further demonstrated that when the player drives back to the shore, blood splatters under his bike and the pedestrian model reappears dead under the bike, the model repeatedly dissipates and returns to life. Another glitch is that on rare occasions, the pedestrian with the player can't be shot and keeps vanishing.
Technically, it is an uncommon glitch. A rational explanation would be that the game developers didn't produce a code for driving with the pedestrians into the shallow waters. This could be the reason that the pedestrian model causes multiple errors.