The Dry Ocean Quest can be started by speaking with any Elder God, while they are visiting Kotana. Items needed: Bucket of Water, 6 Godstones, Bucket of Lava, 3 Cocoa Beans. Official Quest difficulty: Medium.
Speak to an Elder God while they are in or near Kotana to start the Quest. The God will say that "The Villagers look worried about something, but I don't know if I should say..." Say you want to help, and he will explain, to an extent... "Take this Ritual Book, follow it carefully, and execute it." The Ritual Book must be given back at the end of the Quest. Follow it carefully, that's all that can be said. One mess up, and the Villagers will hate you. Once you finish the ritual, the Lava on the Island will disappear, and the God will thank you. You give back the Book, and claim the reward.
At this point you have beat the Quest!