Underground Copper Pipe in Shore Environment

I own a vacation home on the New Jersey shore. The water main coming to the house just broke, (37 year old galvanized piping). No surprise we are the 6th on our street this year.
I hired a contractor who agreed to replace the entire main (20') with a black flexible pipe up into the crawl space. Initially he told me that all things corrode in this environment, (even copper), and recommended this plastic material which they seem to use on all new construction here.
Upon doing the job he told me that the galvanized pipe was attached to flexible copper piping directly in front of the house so he didn't need to replace small piece of copper as it is in fine shape.
Is it true that copper will break down in a shore community with high ground water, prone to flooding, and salt content? Should I be concerned about this few feet of copper that is remaining?
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