That thing is called a Secchi-disc, and it’s used to determine the opacity of the seawater. The size and the color are standardized, and you lower it as deep as you can see it. (Photo: Metsähallitus / Suvi Saarnio)
This blog uses cookies, like every damn website out there. If you're annoyed about these notifications, yeah, so am I. Let's hope whoever came up with this will stub their toe 10 times per day.OkRead more