Polish Navy
In the fifteenth century there was a small force of ships that primarily operated on rivers and lakes. In 1454, the  city of Gdańsk was back in Poland after being previously occupied by the Teutonic Knights since 1308.  Gdańsk is a seaport so Poland could have a large fleet on the Baltic. In 1561, following a victory over a Russian fleet in the Baltic, the Polish Navy got a second  port at Riga, in modern-day Latvia. The Polish navy won the Battle of Oliwa in 1627 against the Swedish Empire, during the Polish–Swedish War.  The Polish–Lithuanian Commonwealth never really had a strong navy.