The river ditching doesnt sound so good, chances are you will find youself upside down on the water (for anything with fixed gear or gear out). Dont think its too easy to ground loop a tricycle but you can get a bit of sideways movement on a soft surface by use of rudder and brakes. Full back stick will indeed help keep the weight on the mains for braking. I wouldn't like to load up the nose wheel at any time let alone when trying to induce a ground loop.