What an unfortunate interruption to an episode of skinny-dipping on an alien planet, painted by Mel Hunter (1927-2004) for the April 1957 cover of If: Worlds of Science Fiction. Alien pervs seem to have been a thing with old Mel, as suggested by the earlier illustration to the right, also done by him (source: Wikipedia).

This issue of If: Worlds of Science Fiction is available to read and download at the Internet Archive.