Norma Roche writes in Mythlore that Tolkien makes use of the medieval story of the voyages of Saint Brendan and the Irish Immram tradition, where a hero sails to the Otherworld, for his vision of the Blessed Realm and seas to the west of Middle-earth, as seen in poems such as The Sea-Bell and Imram, while (as several scholars note) his Fastitocalon resembles the tale of Jasconius the whale.