At many bathing spots on the Unterhavel and Dahme rivers, dryness and heat as well as water temperatures of up to 25 degrees have encouraged algae growth in recent weeks. Warnings about blue-green algae were issued there from mid-July. There are currently still warnings for the Schmöckwitz, Kleine Badewiese, Grunewaldturm and Breitehorn bathing areas due to the development of blue-green algae and low visibility. Cercariae, larvae of small sucking worms, have also been found at some bathing spots. They can cause so-called bathing dermatitis in the form of a skin rash.