This roadside attraction about an hour north of Tampa, Florida began operating in 1947. The main feature of the park, which included a natural spring, was the Mermaid Theater, featuring lovely ladies who frolicked underwater, using special air hoses to breath. The place was at its most popular in the 50's and 60's when elaborately staged underwater shows regularly played to sold out crowds.
Today, the park is run as a state park, and there's water slides and flume ride. And the mermaids live on, since mermaids live forever.
Check out this video: