( ( Air bubbles ) ( ( mark ( ( the trail ) ( of ( the ( approaching ( underwater figure ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Air) (NNS bubbles)) (VP (VBP mark) (NP (NP (DT the) (NN trail)) (PP (IN of) (NP (DT the) (JJ approaching) (JJ underwater) (NN figure))))) (. .)))
Air bubbles mark the trail of the approaching underwater figure.
(ROOT (S (NP (DT An) (JJ underwater) (NN spider)) (VP (VBZ uses) (NP (JJ shiny) (NN air) (NN bubble) (S (VP (TO to) (VP (VP (VB breathe)) (CC and) (VP (VB keep) (ADJP (JJ alive)))))))) (. .)))