And yet you can't provide a link or citation for that alleged USCG official position.

Even the age of long gone fossil Oceans, such as the Tethy's Sea, are well known.  Continents move during geological time. Oceans open and close as that happens.

https://en.wikipedia.org/wiki/Western_Interior_Seaway

https://www.britannica.com/place/Tethys-Sea

USA Navy Chief Navigator / Oceanographer Tilly, appearing in uniform and identifying himself by name, Rank and Assignment, describing his transition from Climate Change Skeptic to accepting the observed fact of climate change and sea level rise. 

He gets questions from Denier Doofuses asking what the big deal is, won't USA Navy ships just float higher on the rising seal levels. -)

https://climatecrocks.com/2011/03/05/admiral-david-titley-us-navy-chief-oceanographer-i-used-to-be-a-climate-skeptic/

https://climatecrocks.com/2011/03/05/climate-change-impacts-on-us-naval-operations-admiral-david-titley/