Eggs (Symbol)
Eggs help build the bond between Elisa and the creature, and as her courtship of him progresses, she brings him more and more eggs each day. Eggs are used here as symbol of female fertility, and in turn set the stage for an inversion of conventional gender roles, as Elisa pursues the male in this situation.
Date and Time (Motif)
We're constantly given a firm sense of time in the film, whether it's the date that Elisa will return the creature to the water, the number of hours General Hoyt gives Strickland to find the creature, or the midnight punch-in which Elisa barely just makes every night at her job. It's a clever narrative device that roots the characters in this fantastical fairytale in a very practical reality.
Samson and Delilah (Allegory)
Zelda and Strickland's rapport almost entirely consists of telling each other the story of Samson and Delilah from the Bible. It's sparked when Zelda says her middle name Delilah comes from the Bible, and she recounts the story to Strickland in an effort to show him that no matter how strong he thinks he is, a woman can rob him of that strength. Later in the movie—while interrogating her in her houseStrickland rebuts Zelda's telling by talking about the end of the story when Samson regains his strength and gets his revenge. Strickland, obviously, construes himself as that version of Samson, and for a moment it seems like he's on the money.
Aquatic Blue (Motif)
An aquatic blue saturates much of the movie, from the underwater opening shot to the walls of the laboratory building to the color of the creature's skin to the paint job on Strickland's car. Given Guillermo del Toro's poetic sensibilities, this motif could be in the service of a simple visual flourish, or to trace a thematic unity throughout the film.
Water (Symbol)
Water, simply, equates to life in the film. Any time the creature is in water, he is safe and secure, and any time when he is out, he's in danger. Consider, too, the love scene in the bathroom, when Elisa fills the entire room with so much water that it pours out through the door and drips to the theater below. Here, we see the two seemingly incompatible creatures undertake a life-making act. At the end of the film, when the creature heals Elisa, he gives her a second life as a being that can breathe underwater.
