It just so happens that some of us have some pretty fond memories of staying up late, long after our parents went to bed, to watch this exploitation classic and thus learning a few things about the possibilities of human/humanoid-fish-creature crossbreeding. Ahem.
Anyway, even if we didn't have such nostalgia for the film, anyone can see it's a pretty kick ass poster that was just begging to be repurposed. Good choice of fonts, too, which complement and work well with the original text left on the poster. It certainly caught our attention -- and now we have t go dig up the battered copy of the movie we have hidden somewhere and rewatch it...