( ( ( The velocity ) ( of sound ) ) ( ( slows ( as ( ( the ( water temperature ) ) ( decreases ( approaching ( the thermocline ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN velocity)) (PP (IN of) (NP (NN sound)))) (VP (VBZ slows) (SBAR (IN as) (S (NP (DT the) (NN water) (NN temperature)) (VP (VBZ decreases) (S (VP (VBG approaching) (NP (DT the) (NN thermocline)))))))) (. .)))
The velocity of sound slows as the water temperature decreases approaching the thermocline.
(ROOT (S (PP (IN As) (NP (NP (DT the) (NN temperature)) (PP (IN of) (NP (NN water) (NNS decreases))))) (, ,) (NP (DT the) (NN water) (NNS molecules)) (VP (VB slow) (PRT (RP down))) (. .)))