The Underwater Ruin is a ruin of an ancient civilization sunken deep beneath Moga Island. The Elder Dragon, Ceadeus, makes its home here along with Goldbeard Ceadeus and the Abyssal Lagiacrus. There is a shortcut from base camp to Areas 2 and 3 available when you have repelled Ceadeus. The battle soundtrack of Underwater Ruin is the same as the Tower's battle soundtrack. A Dragonator and two ballistae are found in these ruins,supposedly built by the old ancestors of the Moga Village Chief to keep monsters, like Ceadeus, at bay.
These are the lyrics to the song that is played in the Underwater Ruins. Taken from the Hunter's Encyclopedia 3.
Song of Life
We ask of the meaning of life