How does the author use foreshadowing in Kon-Tiki: Across the Pacific by Raft?

In Chapter Six, the crew decides to always keep a line tied to the raft and dinghy, as losing the raft would prove deadly. Thor reflects that falling overboard would also be disastrous, as the raft cannot stop or go back to pick up a lost crewmember, foreshadowing an event to come.