Simile

Bringing two different things together with an explicit word, such as "like," "just as," or "seems." Unlike the metaphor, the comparison makes it plain that there are two things.

In Dom Casmurro

Eyes of undertow? Well, undertow. That's the idea I get of that new expression. They carried some mysterious, forceful fluid, a force that pulled inward, like the wave that recedes from the beach on days of undertow.

"Like the wave that recedes from the beach" makes the comparison explicit and sharpens the force: the movement of the wave that pulls inward whoever stands at the water's edge, which the narrator details so the reader can feel the effect.

Chapters XXIII to XXXIV: The Gypsy Eyes and the Eyes of Undertow, the narrator

His name was Ezequiel de Sousa Escobar. He was a slender young man, with light eyes, a little evasive, like his hands, like his feet, like his speech, like everything.

Chapters LIV to LXV: The Seminary, Escobar, and the Iago Thread, the narrator

Capitu's eyes gazed at the dead man, like the widow's, without her weeping or words, but wide and open; like the sea's wave out there, as if it wanted to swallow the morning swimmer too

Chapters CXIII to CXXIV: Sancha's Hand and the Drowning, the narrator

one was inside the other, like the fruit inside the peel

Chapters CXXXVI to CXLVIII: The Cup, the Separation, and the Rest, the narrator