Water Medallion

The Water Medallion is an item in The Legend of Zelda: Ocarina of Time.

In-game
After defeating Morpha in the Water Temple, Link receives this medallion from Ruto, the water sage. Though it has no known purposes besides marking Link's quest progression, some have theorized it may have had some additional purposes before the game was released. It's a circular blue medallion with a flower-like shape on it.