The eleventh and twelfth centuries have traditionally been interpreted as the era when the Byzantine navy declined, and then was allowed to disappear. Historians often mark the death knell of the Byzantine navy with Emperor John II Komnenos ending the collection of taxes for localized defence fleets. Niketas Choniates describes the act as a money-hungry measure devised by the finance minister John of Poutza, whereby fleet taxes would be collected and spent centrally, leading to the end of localized fleets as funds were diverted to other sectors. This reform has traditionally been interpreted as one that led to losing a war with Venice in the 1120s, provincial insecurity, the eventual outsourcing of the Byzantine navy to the Italians, and finally the sack of Constantinople itself by the forces of the Fourth Crusade when the Italians turned against them.Such an interpretation does not however sit easily with the reign of John II Komnenos, during which on numerous occasions the navy is referenced as playing a crucial part in the emperor’s campaigns, a feature that began in Alexios’ reign and continued into Manuel’s. Though Pryor and Jeffreys have previously expressed doubt that such a centralising naval reform could really spell the end of the Byzantine fleet, and possibly the empire itself, this paper will build upon that doubt with evidence that necessitates a re-evaluation of the traditional interpretation. First, the narrative of John’s war with Venice in the 1120s will be examined, followed by how the subsequent naval reform was shaped by these events, which themselves only confirmed the experiences of the Byzantine Navy in previous decades, and so highlighted the need for reform. This analysis will demonstrate that a centralising reform was a coherent measure undertaken to increase the efficiency of the fleet, and to recognize officially trends in organization that had already emerged under Alexios. Subsequent fleet operations in John and Manuel’s reigns reveal that the role of the navy did indeed change in the early twelfth century, but the narrative of decline is false. Throughout this section it will also be shown that analysis of the Byzantine navy has been overly shaped by use of hostile sources. The second part of this paper will then move on to highlight three major uses of the fleet that have been undervalued by scholars focused on traditional sea battles: its use on rivers as well as the sea, its use for transport and logistics, and its ‘soft power’ diplomatic capacity. The combination of these factors reveal a Byzantine navy that was a crucial part of the Komnenian restoration of Byzantine fortunes in the twelfth century, and that its decline after the death of Manuel must be seen as a product of other factors, rather than a cause of the late twelfth-century imperial decline in itself.