In Arthurian legend, the Fisher King was the guardian of the Holy Grail, but I wasn’t sure how he came by his aquatic nickname until I looked it up today. Since he was severely wounded in either the legs or crotch, he was unable to move around or ride a horse, and hence spent all his time fishing.
How he got the wound varies from one version of the story to another, but one notable telling has it that it was caused by the Holy Spear that pierced the side of Jesus. His infirmity affected his kingdom as well, which became a wasteland. In earlier versions of the legend, it is Sir Perceval who manages to cure the king and heal the land by asking the right questions about various objects in the castle.
At first he fails, but he later returns and gets it right, after which he learns that he is the Fisher King’s grandson and heir to the grail-keeping position. Later versions make Galahad the one who finds the grail and heals the Fisher King, although Perceval and Bors are sometimes his companions. Another oddity of the Fisher King stories is that some divide his character into more than one individual, sometimes locating the Fisher King and the Maimed King in the same castle. The Fisher King has been given several names over the centuries, but his best known is probably Pelles.
Some scholars speculate that the Fisher King is based on a figure from Welsh mythology known as Bran the Blessed, King of Britain. Bran kept a cauldron that could revive the dead, almost certainly the source for the Black Cauldron in Lloyd Alexander’s Prydain series, and was wounded in his foot by a poisoned spear. His wound hurt so much that he begged his friends to kill him. They cut off his head, which usually works pretty well, but in this case the head continued to live and talk for seven more years. Eventually, it was buried at the White Hill, which is said to have been where the Tower of London now stands. There is a Welsh story of King Arthur that has his knights seeking a magic cauldron, and a tale of Perceval in which he finds a severed head at the Fisher King’s castle, both possible transitions between the story of Bran and that of the search for the Grail. Perhaps even more telling is that some versions say the original keeper of the grail, who obtained it from Joseph of Arimathea, was named Bron.
If you liked this, you might also be interested in It’s a Round, Round Table, on King Arthur’s knights, including Perceval and Galahad. I can also remember writing one about holy relics, but for some reason I can’t find it.