3 ms·
It looks like a Secchi disk, used for measuring water turbidity and as a fiducial marker. https://en.wikipedia.org/wiki/Secchi_disk https://en.wikipedia.org/wi
by mrob 7y ago
It looks like a Secchi disk, used for measuring water turbidity and as a fiducial marker.
https://en.wikipedia.org/wiki/Secchi_disk https://en.wikipedia.org/wiki/Secchi_disk