That's an opportunity that very few people have had.
( That ( ( ( 's ( an opportunity ) ) ( that ( ( very ( few people ) ) ( have had ) ) ) ) . ) )
(ROOT (S (NP (DT That)) (VP (VBZ 's) (NP (DT an) (NN opportunity)) (SBAR (IN that) (S (NP (RB very) (JJ few) (NNS people)) (VP (VBP have) (VP (VBN had)))))) (. .)))
Not many people get the chance to swim with sharks. 
( ( Not ( many people ) ) ( ( get ( ( the chance ) ( to ( swim ( with sharks ) ) ) ) ) . ) )
(ROOT (S (NP (RB Not) (JJ many) (NNS people)) (VP (VBP get) (S (NP (DT the) (NN chance)) (VP (TO to) (VP (VB swim) (PP (IN with) (NP (NNS sharks))))))) (. .)))