premise: A boy in an innertube in the pool splashing and smiling.
hypothesis: A boy enjoys himself at the pool.
explanation_1: In both sentences, a boy is in a pool.  The fact that he is smiling shows that he enjoys himself.
explanation_2: SPLASHING AND SMILING MEANS ENJOYING
explanation_3: If the boy is smiling he enjoys himself.
premise_logic: exists e1 e2 x1 x2 x3 x4 x5 x6.(n_pool(x6) & n_pool(x3) & Actor(e2,x4) & v_smile(e2) & in(x4,x5) & in(x5,x6) & n_innertube(x5) & n_boy(x4) & Actor(e1,x1) & v_splash(e1) & in(x1,x2) & in(x2,x3) & n_innertube(x2) & n_boy(x1))
hypothesis_logic: exists e1 x1 x2 x3.(n_pool(x3) & n_male(x2) & at(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_enjoy(e1) & n_boy(x1))