Synesius’ letter to his brother, describing his passage from Alexandria to Cyrene, is a fruitful source of information on seafaring at the turn of the 4th century CE. The present article is an experiment to discover maritime information, based on this source and geographic and climatic facts. The distance from Alexandria to Azarium, the final landfall, is 360 nautical miles, although the distance actually sailed was 400 miles. The sailing, generally against the prevailing wind, lasted seven days, of which two were spent on shore. A log and a chart of the complete passage are suggested. Concentrating on the maritime details reveals the skill of the professional skipper, Amarantus, experienced in navigating these waters.
