Police are on alert that if a body is found floating in the water along Wellington's south coast, it could be fake.

A group of people shooting a movie in Houghton Bay last night had to call police to warn them their fake dead body prop had gone missing.

The group feared it had washed out to sea.

Police would not go looking for the prop, but Inspector Ken Climo said they were aware that if a body was reported to them, it could be fake.