I met a diver visiting from Cayman Islands and he told me about their spearfishing regulations. I heard about places with strict spearfishing regulations before, some places do not allow spearfishing at all. Some like Bahamas allow polespear and sling only. But Cayman Islands has the strangest rules. Apart from their Cayman Islands Protected Areas.pdf where spearfishing is not allowed period, there's only one kind of speargun allowed; an ancient Champion model. No more spearguns, even the same model Champion, can be brought into the country. The old Champion spearguns that are already on the islands can be repaired and modified to some degree. I guess the idea is to allow the grandfathered in spearguns only to be used.
But spearos are resourceful Here's a picture of the old Champion handle. Below it the Beuchat Polynesian and JBL Explorer which are still available. Without getting specific you should get the idea. They're shit spearguns by today's standards. But in Cayman Islands all the fish on a boat on a given day are taken by one
Other rules to note: must be 18 years old and have a license to use a speargun, there's a 3 fish per day limit. Visitors are not allowed to use spearguns at all.