Karasu is a small town in Sakarya province on the Black Sea Coast. With a population of just 30,000 during the winter months, this all changes in the summer when 90% of the population consists of tourists. Karasu is close to Istanbul, Bursa and Ankara and its sandy beaches and well established local tourist facilities have made it a busy tourist destination.

Karasu is trying to gain Blue Flag status for its beaches but it suffers from coastal erosion and there are some pollution issues. There is not a great deal to do and see in Karasu. People come here to relax and spend time on the beach. The Acarlar Floodplain Forest is located here. This natural seaside, lagoon, dunes and forest area stretches up the coast towards Istanbul and is an important wildlife conservation area.

Historically the town was known for its zinc and lead production. Today the focus is on hazelnut farming and tourism.