In this paper, we describe a ballast water data logger system to monitor the ballast water exchange and the water quality contained in ship tanks. This system is able to register physical-chemical parameters of ballast water by using sensors for measuring turbidity, salinity, dissolved oxygen, pH and temperature. Those data are tagged with the geographical position (GPS), date and time at which the ship operates its ballast system and are remotely transferred via satellite transmission to an Internet server. The system was installed on the ship M/V Crateus (from Norsul Navigation Company) and has been functioning since April 2014, collecting ballast water quality parameters in the routes between Argentina and the north region of Brazil. From the collected data, the system proved to be able to identify the ballast water exchange along the ship's journey, allowing for independent verification of information provided by the crew in the ballast water reporting form. As an additional advantage, this information can be automatically transmitted to the port authorities, improving the reliability of this information and reducing, or even removing, the possibility of data tampering. Nowadays, the salinity is the main indicator to determinate whether a ship makes the ballast water exchange. However, we identify that water turbidity can be one more indicator to identify the ballast water exchange that could be recommended by the International Maritime Organization.