I'd never heard of moiré effect beacons until I got an email asking me about them. It seemed like a really clever idea - but it was really hard to research. Or at least it was, until I stumbled upon one magic phrase that revealed its history.
It turns out this thing's called an "Inogon leading mark" or "Inogon light" -- Inogon, not Inogen -- and it's a Swedish invention from the 1980s. But there's still a question: why is being used to mark an undersea cable, instead of guiding people home?
(Full disclosure: there were some weird strobing effects from the light that only showed up when I got the footage into the edit, so the image you see here has been digitally stabilised so it appears the same way on screen as it does in person!)