The Open Boat The Oar

We're introduced to the oars in the fourth paragraph of the story:

 It was a thin little oar and it seemed often ready to snap. (1.4)

With this short little line, Crane manages to up the tension several notches. We may have thought, "Oh, they've got a lifeboat, they can row to shore, they'll be fine." But if the oar snaps, they're done for.

The oar is the men's lifeline; it's what will get them to safety and out of the lifeboat. It's fragility reflects the men's own mental strength and patience throughout their time at sea—despite appearing ready to snap at any moment, it must remain strong and whole to get them to safety.