You can choose to take the boat or ferry to go to Latvia. The ferries depart from North Germany (Kiel, Lubeck and Rostock) to Liepaja, Riga and Klaipeda in Lithuania. The time on the boat is approximately 24 hours. The distance to Kuldiga is still 90 km (from Liepaja), is 150 km from Riga and from Klaipeda is about 190 km.
Information and bookings via www.balticferries.nl