Which figure of speech is used in the phrase "babes of the sea"?

The options were:

pace simile diction metaphor syntax

The correct answer is metaphor. This question refers to "The Open Boat" by Stephen Crane:

"The correspondent looked over his shoulder at the captain. His face was hidden, and he seemed to be asleep. He looked at the babes of the sea."

Stephen Crane uses naturalism to personify nature and to reveal his personal feelings of overwhelming insignificance in the face of nature. Crane humanizes nature many times throughout his story.

Metaphor is a form of figurative language, which refers to words/expressions that mean something different from their literal definition.