(S (S (BASENP (NNS Scientists)) (VP (VBP have) (VP (ADVP (RB also)) (VP (VBN reported) (NP (BASENP (JJ immense) (JJ underwater) (NNS plumes)) (PP (IN of) (NP (BASENP (VBN dissolved) (NN oil)) (RRC (ADJP (RB not) (JJ visible)) (PP (IN at) (BASENP (DT the) (NN surface))))))))))) (PERIOD .))