Marathon, Florida - About 70 rough-toothed dolphins beached themselves in the Florida Keys Thursday, a day after the USS Philadelphia had conducted exercises with Navy SEALs in the area. Many scientists claim that loud bursts of sonar used by naval vessels, disorient marine mammals, causing them to surface too quickly and suffer the equivalent of what divers know as the bends when sudden decompression forms nitrogen bubbles in tissue. This they believe is the reason dolphins and other marine animals beach themselves. At least 20 of dolphins who beached themselves have died so far. Navy officials have refused to say if they used sonar during the exercise.