premise: A boy at the beach runs through the surf towards three other people who are already in the water. hypothesis: A boy can't swim so he didn't go to the beach with his family.
contradiction: If the boy didn't go to the beach he cannot be at the beach.|contradiction: The boy can't swim and didn't go to the beach so there is no way he could be running towards people in the water.|contradiction: The boy either stayed at home or went to the beach with his family.