Location: Santa Modesta
From the landing spot in the middle of the town, head towards the ocean where you should find a diner between you and the beach. As you reach the beach, you should find a lifeguard tower with a sign asking you not to feed the sharks. What you'll want to do is the opposite by picking up one of the humans and throwing them off into the water in the distance. It might take a few seconds after, but you'll get the trophy from doing this action.