( ( Each boat ) ( ( creates ( ( ( a ( bow wave ) ) and ) ( a ( stern wave ) ) ) ) . ) )
(ROOT (S (NP (DT Each) (NN boat)) (VP (VBZ creates) (NP (NP (DT a) (NN bow) (NN wave)) (CC and) (NP (DT a) (JJ stern) (NN wave)))) (. .)))
Each boat creates a bow wave and a stern wave.
(ROOT (S (NP (DT A) (NN bow) (NN wake)) (VP (VBZ is) (VP (VBN created) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN wave) (NN source)) (VP (VBZ moves) (ADVP (RBR faster)) (PP (IN than) (NP (DT the) (NN wave) (NN propagation) (NN speed)))))))) (. .)))