Michael of Rhodes signed onto a Venetian galley in 1401 as a common oarsman. Over the next four decades he sailed on dozens of voyages, either in the war galleys of the Venetian navy, or in the commercial galleys of the merchant fleet. He rose in the ranks, attaining a number of different offices, including the highest rank a non-noble could have in Venetian service.

Michael documented his life and knowledge in a remarkable manuscript. Only recently rediscovered, it chronicles Michael's service record and includes more than 200 pages of commercial and calendrical computations, a beautifully illustrated section on astrology, some of the earliest surviving portolan aids to navigation, and the world's first known treatise on shipbuilding.