the water-eaten log the fouled compass (lines 85-86)
These are both images of the power of nature and the weak, and the temporary nature of human creations. Ships are meant to resist nature, to hold out the water and make it possible to live in the ocean, where nature usually runs the show. But when something goes wrong, nature starts to take over immediately. When the ship is still floating, we use compasses to figure out where we are going and logs (here that means something like a ship's diary) to see where we've been. Once the ship sinks, nature attacks and eventually destroys the human instruments. These ruined things are a way for Rich to talk about the destructive power of nature, even when we try our best to protect ourselves from disasters.