Recent geoarchaeological research has revealed that the Gulf of Cadiz was struck at least once by a large tsunami during the Phoenician period, roughly between the 8th and 3rd centuries BCE. In this contribution, at attempt is made to reconstruct the religious reactions of the Phoenician communities of Iberia and, specifically, those of Gadir, in the wake of cataclysms of this type, revolving around the city’s tutelary god Melqart. The Ugaritic tale of the conflict between Baal and Yam and the biblical tradition in the account of Yahweh’s struggle against the sea reveal a way of representing the containment of the forces of ocean chaos through the establishment of a cosmic boundary. After the catastrophic events unfolding in the Gulf of Cadiz, the Baalic attributes of the Melqart of Gadir must surely have been emphasised in an account in which he is attributed with the victory over the forces of ocean chaos and, by his divine command, the establishment of a cosmic boundary of containment and perpetual protection against the threat posed by the sea. This account, which is apparently echoed in Pindar, Strabo and Philostratus, may be at the root of the ancient and medieval notion of Gades as the edge of the world.