( ( In ( the crowd ) ) ( , ( ( ( about ( a dozen ) ) sailors ) ( ( were ( ( ( ( holding ( a body ) ) aloft ) , ) ( ( ( an ( incredible feat ) ) ( of strength ) ) ( considering ( they ( ( were all ) ( ( ( treading water ) furiously ) ( to ( ( stay afloat ) ( beneath ( the ( added weight ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (DT the) (NN crowd))) (, ,) (NP (QP (RB about) (DT a) (NN dozen)) (NNS sailors)) (VP (VBD were) (VP (VBG holding) (NP (DT a) (NN body)) (ADVP (RB aloft)) (, ,) (S (NP (NP (DT an) (JJ incredible) (NN feat)) (PP (IN of) (NP (NN strength)))) (VP (VBG considering) (SBAR (S (NP (PRP they)) (VP (VBD were) (RB all) (VP (VBG treading) (NP (NN water)) (ADVP (RB furiously)) (S (VP (TO to) (VP (VB stay) (ADJP (RB afloat)) (PP (IN beneath) (NP (DT the) (VBN added) (NN weight)))))))))))))) (. .)))
In the crowd, about a dozen sailors were holding a body aloft, an incredible feat of strength considering they were all treading water furiously to stay afloat beneath the added weight.
(ROOT (S (NP (NNP Birds)) (VP (VBP need) (NP (DT a) (JJ light-weight) (NN body)) (PP (IN for)) (S (VP (TO to) (VP (VB stay) (ADVP (RB aloft)))))) (. .)))