When considering the sex appeal of amphibious monsters, everyone knows it's critical to make sure they have a few well-developed assets: great gills, bioluminescent skin, cool eyes and, of course, a fantastic butt.

That last one was more important than ever in Guillermo del Toro's latest, The Shape of Water, where having a "great butt" was a key attribute of the film's creature, according to the official art book The Shape of Water: Creating a Fairy Tale for Trouble Times.

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Del Toro explained:

“Every female in the del Toro household was crucial, too much derriere, not enough derriere, the shoulders are not beautiful enough.’ The butt we show abundantly in the movie. It was a very delicate sculpture process because it always had to be run by my household.”

All told, the process of finalizing the fishman's design took upwards of three years, according to Del Toro, one of the longest deliberations of his career -- "some kind of record!"

RELATED: Del Toro Insisted, The Shape Of Water Is NOT An Abe Sapien Movie

Del Toro and his visual effects team's work paid off. The Shape of Water recently opened nationwide to resoundingly positive reviews, earning it a 93% Certified Fresh rating on Rotten Tomatoes, no doubt thanks in part to the wonderfully designed monster behind.

The Shape of Water stars Sally Hawkins, Michael Shannon and Octavia Spencer, with Doug Jones embodying the aforementioned wonderfully proportioned fishman.

(via Syfywire)