Dolphins sometimes have rather strange dorsal fins.
The curled dorsal fin of this striped dolphin (click on photo to enlarge) was photographed in the Gulf of Corinth, Greece, in the context of Tethys' Ionian Dolphin Project.
Physical anomalies are not so uncommon in the Gulf of Corinth, and have been observed on both striped dolphins and bottlenose dolphins.
This particular individual has been nicknamed 'Curley'. We do not know what may have caused this deformity. In any case, Curley looked as fit as any other dolphin in the group.