What does Noah discover when he wades into the water at Thunder Beach to retrieve an aluminum can? Why does he go back in the water a second time? (Chapter 12)

When Noah waded out into the water to get the beer can, he realized that he was walking in water that "had a darkish yellow tint. Strands and clots of foul, muddy-looking matter floated here and there". He was walking in the dumping of fecal matter from the Coral Queen.