Daryl Hannah as the beautiful mermaid 'Madison' in the 1984 film, "Splash"
Source: Reddit
Not only was the 1984 movie Splash a breakout role for Daryl Hannah - but it also cemented the careers of Tom Hanks and director Ron Howard; not to mention great cameos from SCTV alumni John Candy, and Eugene Levy.
Academy Award-winning visual effects artist Robert Short created and designed Darryl Hannah's mermaid tail - which was fully functional. Hannah could swim so fast with the special tail that her safety team couldn't keep up with her. At the end of a scene, the tail was difficult to remove - so Hannah would keep it on while the cast ate lunch.