Its way not OK to loot the reef. Removing canons, anchors and such have jail sentences attached to them. After they are in someones possession, however acquired, they can't be bought or sold under the law.
No one is going to put two tons of old canon in a government vault. If the person in possession manages to get them registered the government usually allows them to stay on the property. The trick is gona be registering them with out incriminating your self.
http://www.biodiversity.bz/downloads/laws/ancient_act.pdf
Having them cleaned in you back yard is going to hard to explain.
It would eliminate excuses like 'been in the family a long time'.

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