She plans to join her rowing pals in the 132-mile Great River Amazon Raft Race in Peru – for which organisers boast "the faint-hearted need not apply".
Kate, who is dating Prince William, was forced to pull out of a cross-Channel boat race with the group, known as The Sisterhood, last year after Royal concerns.
But she has told her pals she is "thrilled" to be with them for the September race, in which each four-person crew build their raft using logs and jungle vines.
One past participant said: "The tropical sun is trying to boil your brains. Piranhas are waiting to nibble your toes. This is one of the last great adventures."
The Peruvian Coast Guard usually provides safety boats, but with Kate, 26, racing security is sure to be stepped up.
A race insider insisted: "Kate doesn’t want any preferential treatment."
Click here to read more about the The Great Amazon River Raft Race.