In J.R.R. Tolkien’s The Silmarillion, Ulmo is the Vala associated with the sea. He is called the Lord of Waters and governs the waters of Arda, including the seas, rivers, and springs.
Ulmo is one of the Valar, powerful spiritual beings who enter the world to shape and govern it. Unlike many of the other Valar, he rarely remains in Valinor. He travels through the waters of Middle-earth and maintains contact with the peoples living there, especially when danger threatens.
Ulmo repeatedly helps the Elves and Men of Middle-earth. He warns Turgon and directs the founding of Gondolin, and he supports Tuor’s journey in The Children of Húrin and Unfinished Tales. Ulmo should not be confused with Manwë, who is associated with air and the sky, or Aulë, who is associated with craftsmanship and substances of the earth.