What discoveries did the boys make on their boat expedition?For instance, what are the new signs of human habitation found on Coral Island?

In Golding's Lord of the Flies, two
expeditions are described, but neither involves a boat.  The first expedition occurs
early in the book, and is one of Ralph's first decisions as chief--to explore the
island.  On this expedition, he takes Jack and Simon.  They spot the candle-buds that
Simon recognizes, they roll a rock, and discover Castle Rock. The island is untouched by
humans.  They return from the expedition thinking the island is a friendly
one.

The second expedition occurs after Sam and Eric spot
what they think is the beast.  Ralph, Jack, and initially Simon go on this expedition.
 Simon, however, goes back to camp to see about Piggy and Roger comes to take his place.
 In this expedition, the island becomes dark and ominous.  Jack passes by a huge rock
and still wants to roll it.  He thinks Castle Rock would be a great place for a fort.
 But during this expedition, Ralph and Jack spot the parachute of the dead man.  They
see it billowing in the wind, and because it is dark and they are already frightened,
they believe that this parachute is a beast and run back to tell the others.  This event
is what eventually divides the boys and causes Jack's rise to
power.