Ecocritical thinking has sensitized us more than ever before to the tremendous importance of water for human life, as it is richly reflected in the world of literature. The great relevance of water also in the Middle Ages might come as a surprise for many readers, but the evidence assembled here confirms that also medieval poets were keenly aware of the importance of water to sustain all life, to provide understanding of life’s secrets, to mirror love, and to connect the individual with God. In eleven chapters major medieval European authors and their works are discussed here, taking us from the world of Old Norse to Irish and Latin literature, to German, French, English, and Italian romances and other narratives.