The story of Zuisenmon is not complete without mention of Ryuhi. "Zuisen" means a spring of delicious water. The word refers particularly to the spring of pure water than can be seen welling up off on the right side as you climb the stone steps to Zuisenmon. This spring's famous water was praised by the Sapposhi (Chinese envoys) and was henceforth delivered daily to their lodgings at the Tenshikan near Naha Port.

The water gushed forth from the mouth of a stone-carved dragon, hence the name "Ryuhi," or dragon tub.