(S (S (S (BASENP (DT The) (JJ exact) (NN cause)) (VP (VBZ is) (ADJP (JJ unknown)))) (COLON -) (S (NP (BASENP (NNS suggestions)) (PP (IN from) (BASENP (NNS eyewitnesses)))) (VP (VBP include) (S (S (BASENP (DT the) (NN boat)) (VP (ADVP (RB suddenly)) (VP (VP (VBG turning) (ADVP (RB left))) (COMMA ,) (VP (VBG being) (VP (VBN hit) (PP (IN by) (BASENP (DT a) (NN wave)))))))) (CONJP (COMMA ,) (CC and)) (S (NP (BASENP (NN many)) (PP (IN of) (BASENP (DT the) (NNS passengers)))) (VP (VP (VBG moving) (PP (TO to) (NP (BASENP (NN one) (NN side)) (PP (IN of) (BASENP (DT the) (NN boat)))))) (ADVP (RB together)))))))) (PERIOD .))