Go southwest, or so the arrows seem to suggest. What do the arrows point to? Jakarta, on the island of Java, in the Java Sea, but that’s merely coincidental. This is an area where mangrove roots nurture and protect all sorts of aquatic life. So, the big fish work their way into the mangrove forest for a snack during high tide, and then swim back out to the ocean. But then they run into these long fences made of bamboo as they travel back out to sea and follow the fence into the point of the arrow. A little hut is built at the very tippy point of the arrow where the fish will concentrate as they try to make it back out to sea. And then, somehow with nets or a collapsible fence, they haul in the fish.
BUT WHAT ARE THE IMPLICATIONS TO WORLD BUILDING? Ecology, and a culture built on a fishery. Enterprising people develop ways to make life easier for themselves. Each one of these little arrows (I could imagine) would be maintained by a family or several families. Fishing is also a group effort.