A guy in his 20-30’s suddenly feels a “ripple” and is transformed into another identity, another situation, and totally different place within the United States. It was paperback, I read it in the late 1960’s – 1970’s in English. Sci- fi main character this one guy, one scene: he leaves his clothes on the bank of a pond to go skinny dipping with a friend (a woman), they go under water and feel the “ripple” and then when they come up out of the water they are somewhere else, with no clothes. They catch a ride with a man in a pickup truck. Another scene he is in Hawaii with a group of people getting ready to walk on a bed of hot coals.