( ( If ( you ( can ( see ( the fish ) ) ) ) ) ( , ( ( look ( for ( signs ( of ( frost ( or ( ice crystals ) ) ) ) ) ) ) . ) ) )
(ROOT (S (SBAR (IN If) (S (NP (PRP you)) (VP (MD can) (VP (VB see) (NP (DT the) (NN fish)))))) (, ,) (VP (VB look) (PP (IN for) (NP (NP (NNS signs)) (PP (IN of) (NP (NN frost) (CC or) (NN ice) (NNS crystals)))))) (. .)))
If you can see the fish, look for signs of frost or ice crystals.
(ROOT (S (NP (NP (DT The) (NN ice) (NNS crystals)) (SBAR (WHNP (WDT that)) (S (VP (VBP form) (PP (IN on) (NP (DT the) (NN ground))))))) (VP (VBP are) (VP (VBN called) (S (ADJP (JJ frost))))) (. .)))