In "Sinking Islands" by Cai Emmons, the simile "like someone swimming the breaststroke" suggests that the eagle is moving with a certain grace and deliberate control. The breaststroke is a swimming style characterized by smooth, powerful movements that require coordination and effort, allowing the swimmer to glide through the water while maintaining a steady pace.
By comparing the eagle's movement to this style of swimming, the author implies that the eagle is navigating its environment with both power and elegance. It might also suggest the eagle's ability to thrive and maneuver effectively despite challenges, similar to how a swimmer must adjust their technique to move efficiently through water. This imagery enhances the reader's understanding of the eagle as a strong and skilled creature, capable of overcoming obstacles in its surroundings.