LAVA FALLS RAPID, COLORADO RIVER, IN THE GRAND CANYON, ARIZONA   LAVA FALLS RAPID DROPS A TOTAL OF 37 FEET IN LESS THAN A QUARTER OF A MILE. ON THE "DESERET" SCALE OF RATING BIG WATER, LAVA FALLS IS ALWAYS RATED A "10" -- THE MOST DIFFICULT -- AT ALL WATER LEVELS.   THE BELOW PHOTOS WERE TAKEN IN OCTOBER, 1990, OF GROG'S RUN DOWN LAVA FALLS RAPID. THE WATER LEVEL WAS RELATIVELY LOW -- 3,000 CUBIC FEET PER SECOND.   Down the tongue!   Where did my boat go?       So far, so good!       Dive! Dive!   Oh Sh*t! I didn't come on this river trip to get wet!   Surface! Surface! Surface!   Whew! Made it one more time! Still upright!   (Photos Courtesy of Dan Villamaire, River Runner and Professional Photographer, Aspen, Colorado)