Mermaid

Martha is the mermaid who inhabits Martha's Bay, the body of water on Koholint Island that is named after her.

Schule Donavitch made a statue of her, "The Mourning Mermaid" placed near Martha's Bay, but it is not complete. She asks Link to retrieve her lost necklace. When Link returns her the necklace, she rewards him with one of the scales from her tail. Link can place the scale on the Mermaid Statue to reveal a hidden passage where he finds the Magnifying Lens.

Trivia
In the Japanese and some European versions of the game, Link instead had to find her lost swimsuit top, but Nintendo of America deemed this to be too inappropriate for American audiences.