PERKASA ANCHOR CHAIN ARRANGEMENT
I have no knowledge how this was done full size but for your model get some thin wire and loop it around a link of the chain drill a hole in the deck and glue the wire into the hole.
Repeat as often as you think needful. Done carefully you have an invisible but secure fixing.
"that's not a bug its just an undocumented creature."
Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)