( ( If ( ( the waves ) ( are ( not ( ( ( breaking , ) but ) ( moving ( in ( gentle movement ) ) ) ) ) ) ) ) ( ( -LRB- ( ( oscillating waves ) -RRB- ) ) ( ( ( ( they ( leave ( symmetrical ( ripple marks ) ) ) ) and ) ( ( if ( ( ( the crest ) ( of ( the waves ) ) ) ( override ( their ( low ( ( points or ) troughs ) ) ) ) ) ) ( , ( they ( leave ( asymmetrical ( ripple marks ) ) ) ) ) ) ) . ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT the) (NNS waves)) (VP (VBP are) (VP (RB not) (S (VP (VP (VBG breaking)) (, ,) (CC but) (VP (VBG moving) (PP (IN in) (NP (JJ gentle) (NN movement)))))))))) (PRN (-LRB- -LRB-) (S (VP (VBG oscillating) (NP (NNS waves)))) (-RRB- -RRB-)) (S (NP (PRP they)) (VP (VBP leave) (NP (JJ symmetrical) (JJ ripple) (NNS marks)))) (CC and) (S (SBAR (IN if) (S (NP (NP (DT the) (NN crest)) (PP (IN of) (NP (DT the) (NNS waves)))) (VP (VB override) (NP (PRP$ their) (JJ low) (NNS points) (CC or) (NNS troughs))))) (, ,) (NP (PRP they)) (VP (VBP leave) (NP (JJ asymmetrical) (JJ ripple) (NNS marks)))) (. .)))
If the waves are not breaking, but moving in gentle movement (oscillating waves) they leave symmetrical ripple marks and if the crest of the waves override their low points or troughs, they leave asymmetrical ripple marks.
(ROOT (S (PP (IN In) (NP (DT an) (JJ electromagnetic) (NN wave))) (, ,) (NP (DT the) (NNS crests) (CC and) (NNS troughs)) (VP (VBP represent) (S (VP (VBG oscillating) (NP (NNS fields))))) (. .)))