U20 Sunken Submarine

U20 is one of the German submarines that operated against British naval forces in the North Sea during the early stages of World War II. Later in the war, this submarine was transferred to the Black Sea and was scuttled by its crew off the coast of Karasu in 1944. This decision, made to prevent it from falling into enemy hands, left the submarine to the cold waters of the Black Sea for decades.

Today, the submarine lies at a 35-degree angle, 2.5 kilometers offshore and 23 meters deep, near where the Sakarya River meets the Black Sea. Although its structure is largely preserved, it is known to have been subjected to intense fishing net pressure over the years, which has damaged the wreck. METU Institute of Marine Sciences and environmental organizations have carried out various studies to protect the submarine.

The weather and sea conditions in the Black Sea can be quite harsh, especially in autumn and winter. The most suitable period for diving is between June and September, when the sea calms down and visibility increases. During this period, water temperatures also reach more acceptable levels. The number of clubs organizing diving trips in the region also increases in the summer months, which makes planning easier.

The Black Sea is prone to sudden weather changes. Always monitor the weather and sea conditions before your diving day.

Karasu district can be reached from Istanbul by road in approximately 2.5 hours. There are regular bus services from Istanbul to Karasu. Those coming by private car can easily reach Karasu using the D-100 highway.

It is not possible to reach the wreck by land; it requires an approximately 10–15 minute boat trip from Karasu beach. Local companies offering diving organizations usually include boat transfer in their packages. You can contact diving clubs operating in the region in advance for support with both boat and diving equipment.

Since the U20 wreck is located in open sea and at a depth of 23 meters, at least an open water diving certificate is required for diving at this point. It is critically important for safety that inexperienced divers do not dive without a guide.

Fishing net remnants may be found around the wreck. This can restrict maneuverability, especially in narrow areas, and pose a serious danger. Before diving, you should get a briefing from a local guide and ensure that your diving equipment is complete and functional. Also, keep in mind that the Coast Guard periodically conducts inspections in the area.

U20 is an extremely interesting area for underwater photographers. The submarine's hull, periscope remnants, and the community of marine life formed on it open the way for dramatic shots. Since lighting conditions can be challenging at a depth of 23 meters, it is recommended to be experienced in underwater photography and to carry a powerful flash or video light.

The wreck's 35-degree angle allows for impressive compositions with wide-angle lenses. Since visibility in the Black Sea can be lower compared to the Mediterranean or Aegean, choosing calm days in the summer months directly affects photo quality.

There are various hotel and guesthouse options in Karasu district center. Accommodations offering lodging on the Black Sea coast can be a practical choice for divers planning to go out to sea in the morning. In Sakarya city center, there is a wider range of accommodation; however, since the distance to Karasu is approximately 40–50 kilometers, this choice requires transportation planning.

Visitors to Karasu can combine their U20 dive with other natural beauties of Sakarya. The banks of the Sakarya River, Sapanca Lake, and Kocaali beaches are among the prominent spots in the region. Dedicating the morning to diving and then moving to Sapanca Lake in the afternoon can be a good way to make efficient use of the day. The distance between Sakarya and Karasu is approximately 40–50 kilometers and can be covered quickly by car.