premise: a surfer is riding the waves whilst another surfer sits on his board waiting.
hypothesis: A surfer watches as his friend is eaten by a large shark.
explanation_1: The surfer has another surfer sits on his board waiting and this could not have been his friend that is eaten by a large shark.
explanation_2: A surfer can't be riding the waves and watching as his friend is eaten by a shark.
explanation_3: Usually one would be riding and watching at the same time. The surfer would not be sitting on his board waiting and being eaten by a shark at the same time.
premise_logic: exists e1 e3 e2 x1 x2 x3 x4 x5 x6 x7.(n_waiting(x6) & of(x6,x7) & n_board(x7) & of(x6,x3) & n_male(x3) & n_wave(x3) & Theme(e3,x4) & Actor(e3,x1) & v_whilst(e3) & on(e2,x6) & Actor(e2,x5) & v_sit(e2) & (x4 = x5) & n_surfer(x4) & -(x4 = x1) & n_surfer(x1) & n_surfer(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & (x1 = x2))
hypothesis_logic: exists e1 p1 x1 x2.(exists e2 s1 x3.(Actor(e2,x3) & n_shark(x3) & a_large(s1) & Theme(s1,x3) & Theme(e2,x2) & v_eat(e2)) & n_friend(x2) & of(x2,x1) & n_male(x1) & as(e1,p1) & Actor(e1,x1) & v_watch(e1) & n_surfer(x1))