TIMMENDORFER STRAND — An excavator dug an escape channel on Thursday to free a humpback whale stranded for several days on a Baltic Sea sandbank at Timmendorfer Strand beach in Germany. The whale swam through the man-made channel overnight and freed itself.

Coast guard and fire department boats had attempted to create large waves to coax the whale back toward deeper water, but these efforts were unsuccessful. The Baltic Sea lacks strong tides that could have freed the whale without human intervention.

Marine biologist Robert Marc Lehmann guided the excavator digging operations to free the whale. Rescue teams worked with excavators until well after sunset on Thursday but did not free the whale by the time they had to stop work for the night.

Early on Friday morning, the whale was on its way out of Lübeck Bay and was being accompanied by a coast guard ship and several boats, according to Stephanie Gross. A flotilla of vessels followed the whale at a distance after it swam free, hoping to guide it into the North Sea and toward the Atlantic Ocean.

The whale was spotted again at noon in Wismar Bay, near the coastal town of Wismar in Mecklenburg-Pomerania, on Saturday. The whale had been spotted several times in the port of Wismar east of Timmendorfer Strand in recent weeks.

Humpback whales are not native to the Baltic Sea. The whale is 12–15 meters (39–49 feet) long and had developed a skin disease.

The salt concentration in the Baltic Sea is not high enough for the whale to survive long-term. The whale would not be able to find the right kind of nutrition it needs in the Baltic Sea. Male humpback whales tend to migrate.

It was not clear why the whale swam into the Baltic Sea. It was not immediately known if another rescue attempt would be mounted after the whale became stranded again.