( Pumps ( ( kept ( ( the ship ) ( clear ( ( ( until ( ( ( open water ) ( near ( Esopus Island ) ) ) ( was reached ) ) ) , ) ( which ( freed ( ( the ice ) ( that ( had ( ( wedged itself ) ( into ( ( the openings ) ( cut ( in ( the hull ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Pumps)) (VP (VBD kept) (S (NP (DT the) (NN ship)) (ADJP (JJ clear)) (SBAR (SBAR (IN until) (S (NP (NP (JJ open) (NN water)) (PP (IN near) (NP (NNP Esopus) (NNP Island)))) (VP (VBD was) (VP (VBN reached))))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBD freed) (NP (NP (DT the) (NN ice)) (SBAR (WHNP (WDT that)) (S (VP (VBD had) (VP (VBN wedged) (NP (PRP itself)) (PP (IN into) (NP (NP (DT the) (NNS openings)) (VP (VBN cut) (PP (IN in) (NP (DT the) (NN hull))))))))))))))))) (. .)))
Pumps kept the ship clear until open water near Esopus Island was reached, which freed the ice that had wedged itself into the openings cut in the hull.
(ROOT (S (NP (NN Ice) (NN wedging)) (VP (VBZ occurs) (SBAR (IN because) (S (NP (NN water)) (VP (VBZ expands))))) (. .)))