Four women embark on their annual adventure/vacation—whitewater rafting in Maine.  Pia has cooked up this idea and then convinced the other three to go along, as she always does.  Wini, the narrator, is the most skeptical, particularly since their guide is a 20-year-old who, along with his father, is just getting started in the business.  This whole scenario, of course, is a recipe for disaster, but we don’t know if the women’s antagonists will be the forces of Mother Nature or Deliverance-style humans living off the grid.  This novel has strong similarities to Peter Heller’s The River, but in this case the characters are smart women who make some exceedingly unwise decisions.  Disagreements among the women as to the best course of action after each catastrophe (yes, there is more than one) always seem to be resolved by choosing the least reasonable alternative and with Pia continuing to take the lead, despite the fact that she got them into this mess in the first place.  In other words, the plot is gripping, though somewhat frustrating, and the pace is faster than a speeding bullet, with vivid accounts of the women, particularly Wini, fighting for survival, often underwater.  The author doesn’t pull any punches here and delivers a few right to the reader’s gut.  There are times when this novel is not entirely believable, such as when Wini’s knowledge of sign language becomes a life saver, but overall it is very visceral and convincing.