Deep Water
Laura Anne Gilman
 After an oil spill on a nearby Sunnydale beach, Willow discovers a 'selkie'; that is, a girl that can turn into a seal with her sealskin. The selkie, dubbed Ariel by the gang, cannot return to the ocean because her sealskin was damaged by the oil spill. Willow's trying to find a spell to clean it. At the same time, mermaid-like creatures called merrows have come ashore in search of food and the vampire population gets territorial and try to kill the merrows. Buffy and the gang get stuck in the middle of a turf war while trying to save Ariel.