> He also knew the location of the container - in a secluded sea cave accessible only at low tide.
So they've been dealing with this mystery for almost 40 years and this guy knew where the problem was coming from the entire time?
It happens in Engineering all the time too, where you talk to the one user in ten-thousand who happens to have a keen eye for the exact sequence of events on the display, and their careful recitation of the sequence of frames on the display is enough for you to piece together the system state at the time of a failure.
It's rare that engineers talk to users, and it's probably equally rare for environmentalists to talk to individual farmers looking for information.
You can think of there being interaction and coordination graphs with the same nodes. Both are getting bigger (more nodes) and denser (more edges). But the interaction one is getting denser faster.
tl:dr 50/100 years ago it would have been harder to talk to the fisherman, but also way less trash in the ocean to ask about.
Until this became a big campaign with a point of contact and so forth, he probably had no hope of getting any real action, even if he had put it all together mentally and tried to harangue authorities into checking out his theory.