Hanna

"For a very long time... in the water... it was cold... and dark.
 * —Hanna to Eric before going to the afterlife"

Hanna is a girl who drowned when her mother, Lorraine, pushed her off the Little Baroness before the ship disappeared from Toluca Lake in Silent Hill. She appears in Silent Hill: The Arcade as a manifestation or spirit.

Biography
It is implied that Hanna's father was named Jack and he died.

Hanna is a very sickly girl who always stayed inside Brookhaven Hospital due to her condition. It is unknown if she had a terminal disease similar to Mary's, although if she did, this could have been the reason why her mother threw her off the ship, drowning her. This disease may have been tuberculosis, as there is a monster named after it in the game.

One day, Lorraine convinced Hanna to go to Toluca Lake with her. On the Little Baroness, Lorraine pushed Hanna over the edge of the boat, drowning her. Lorraine may have been unable to cope with her daughter's suffering and decided drowning wouldn't delay the inevitable.

Afterwards, Hanna presumably became a spirit haunting the town, uncertain if her mother truly loved her.

Silent Hill: The Arcade
She is the final boss of the game called Phantom, appearing only as a giant rotten head with tentacles, and an arm coming out of her mouth, emerging from the waters of Toluca Lake. The player must defeat her in order to complete the game.

In the Good Ending, she returns to her normal form, and is saved from the town along with Emilie Anderson. After the Captain comforts her, she then re-unites with her mother.

In the Bad Ending, she disappears under Toluca Lake and Eric hears her voice on his radio, and she asks him why he didn't rescue her.

Trivia

 * A similar incident is presented in the events of Silent Hill: Downpour. Ariadne Johnson, an autistic girl, died in a way similar to Hanna by drowning due to her mother's deceit. The player can uncover this story via the sidequest entitled "Ribbons".