Dredgers are a group of specialized mining machines, floating on inland water reservoirs and sea ports, the purpose of which is to extract from the bottom of reservoirs deposits of aggregates (e.g. sand, gravel) or silt that hinder navigation through canals or rivers. The cuttlefish dredger stationed in Mrzeżyno is 30 meters long with a draft of only 1.2 meters and a weight of over 120 tons, and the Kalmar tugboat, thanks to its shape, can move freely and set the dredger in a specific position.