Son of Zeta: Class III After cruising a few kilometers of class II whitewater you will come upon Son of Zeta. It will be identifiable when the river shores close in and compress the Futaleufu. The river makes a zig left and a zag right as the river constricts to create boat-eating whirlpools. The whirlpools in Son of Zeta can take you for a ride but will eventually let you go free. Relax and enjoy the ride.