Lorelei's tail was made of fiberglass and latex. During Lorelei's close-ups, Marta Kristen would wear a costume belt to allow her to use her legs for swimming whenever her character is only seen waist up.
Nancy Sinatra was the original choice to play Sugar Kane. However, she backed out just before production was supposed to begin because a few months earlier her brother Frank Sinatra Jr. was kidnapped and when she found out that part of the plot involved a kidnapping she decided to back out. Interestingly, it would have been her motion picture debut.