sentences:  Polish units involved in scientific diving include the Polish Academy of Sciences in Sopot, and the University of Gdańsk, which carried out biological observations and installed measuring equipment.The Central Maritime Museum of Gdańsk carried out research on a large number of wrecks in the Baltic sea.Other units involved in underwater archaeology and training of divers for this work include the Nicolaus Copernicus University in Toruń and the University of Warsaw.