COPP were "Combined Operations Pilotage Parties".
More information in the "expandable" description for this book:
https://www.amazon.com/Stealthily-Ni.../dp/B00AAMH2O0
Some chapters of the book can be seen here:
https://books.google.com/books?id=0n...0night&f=false
Also quite a bit of info in these links, showing equipment, missions and members of various parties including COPP 6 (COPP VI?) :
http://www.coppheroes.org/index1.htm
https://www.combinedops.com/COPPs.htm
and a brief mention here:
https://en.wikipedia.org/wiki/Amphibious_reconnaissance