The aim of the paper is to analyse the length of time that ships spend in the Port of Gdansk. It is based on the examination of the time when ships come into and leave the port. Source of data used in the study is public web platform - Marine Traffic. Analysis which was conducted, enables to get information about duration of ships servicing in the port with a division into dimension, load capacity and type of the ship. Due to that information, it is possible to observe the duration of complete service for each vessel, including entering the harbour, reloading and the departure. Gained knowledge would allow to forecast, plan and model future development operations more properly. In addition, due to the method based on counting the number of hours that ships spend in the harbour, it is possible to estimate the amount of pollution emitted to the air.