( Breakwaters ( ( are ( structures ( that ( ( protect ( the coast ) ) ( like ( barrier islands ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Breakwaters)) (VP (VBP are) (NP (NP (NNS structures)) (SBAR (WHNP (WDT that)) (S (VP (VB protect) (NP (DT the) (NN coast)) (PP (IN like) (NP (NN barrier) (NNS islands)))))))) (. .)))
Breakwaters are  structures that protect the coast like barrier islands.
(ROOT (S (NP (NP (NNS Structures)) (SBAR (WHNP (WDT that)) (S (VP (VB protect) (NP (DT the) (NN coast)) (PP (IN like) (NP (NN barrier) (NNS islands))))))) (VP (VBP are) (VP (VBN called) (NP (NNS breakwaters)))) (. .)))