If the statement that the Greeks were a people of sailors needs to be qualified, it is nonetheless undeniable that the sea was a geographical aspect of great importance in the ancient Greek world. It is therefore not surprising that this element impregnated the beliefs and cults from the Atlantic to the Persian gulf and in particular in Magna Graecia. This book explores the ways in which the maritime culture influenced the major figures of the Greek pantheon, the Olympian gods, from Homer to the Hellenistic period. It moderates, in this respect, the overimportance too often attributed a priori to Poseidon. An investigation of this type necessarily utilised a variety of sources: literary, epigraphic, archaeological, iconographic and numismatic. By analysing beliefs, the topography of the sanctuaries, cultural practices both on board and on terra firma and the nautical ex voto (anchors and ships), it constitutes an indispensable tool for the study of the Greek religion and the study of naval archaeology.