The Automatic Identification System (AIS) is a collaborative monitoring system designed for collision avoidance in maritime navigation. Originally designed for larger vessels, it is now used by different types of vehicles, from tankers to fishing boats and pleasure crafts. Essentially AIS works on the principle that vessels regularly transmit their current position, along with other characteristics like speed-over-ground, heading and a unique identifier. The abundance of AIS messages have allowed for Geographic Information System (GIS) applications and trajectory analytics to model and describe vessel traffic, extract useful patterns and provide predictions on future trends. To that end, the AegeaNET is an open sensor network composed of AIS and ADS-B receivers, strategically deployed throughout the Aegean Sea. AegeaNET is an academic initiative by the Intelligent Transportation Systems Lab (ITS Lab) of the University of the Aegean (Greece). This network facilitates real-time tracking of maritime activity, providing critical data essential for navigation and safety. We present a publicly accessible dataset originating from a receiver on the island of Syros, covering a large area in the middle of the Aegean sea, including most of the Cyclades. The duration of the dataset is a full three (3) month period, from July to September 2024. The positional messages of all vessels are included in a single AIS file, sorted in ascending order using their respective timestamp. An initial cleaning was performed to remove messages with erroneous or missing critical fields. Finally, for the purpose of anonymity, a masking mechanism was applied on top of the vessel identification field (MMSI).