The Toto Lake is a location from The Legend of Zelda: Breath of the Wild. It is located in the Lanayru Wetlands region of Hyrule. In the middle of the lake are some flooded ruins where Link can lift a metallic Treasure Chest by using the Magnesis Rune. The chest contains the Zora Helm which allows Link to perform the water-based Spin Attack.
According to some of the worn "Zora Stone Monuments" during the related side quest, the Zora Helm was apparently won by Link while driving a Lynel that had threatened Zora's Domain back to Ploymus Mountain. The Helm was later placed within Toto Lake to honor Link's heroic deeds.
Like many locations in Breath of the Wild, Toto Lake is named after a character from a previous game, namely Toto.