Symbolism, Imagery, Allegory
Even Jaws wouldn't want to mess with this guy.
The see-through shark that Tom Stenton brings back from the Mariana Trench is a symbol of Stenton himself—voracious, insatiable, and utterly predatory. More broadly speaking, it's also a symbol of the capitalist greed that Stenton represents, not to mention the ruthlessness of some kinds of corporate wheeling and dealing.
Even worse, this shark is "transparent"—just like the Circle wants us all to be. Unfortunately, it turns out that being transparent doesn't prevent you from being a predator. It just makes you an even better predator.
Near the end of The Circle, Ty Gospodinov refers to his company as "the f***ing shark that eats the world" (2.27.19). Through Stenton's deliberate guidance and Eamon Bailey's misguided idealism, the Circle itself has become an unstoppable force that will devour everything in its path. In this sense, Stenton's transparent shark is also a symbol of the Circle itself.