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Police from two forces searched intensively there for months, using helicopters, sniffer dogs and ground penetrating radar.

But images from the EU's Sentinel radar satellites - which are low resolution but capable of penetrating cloud cover - revealed that the ships were in the military section of the port.

"The water was just repelling off. It wasn't even penetrating or nothing," Hipolito said, referring to the bone-dry earth and brush around the homes.

That "something" can be a Ukrainian drone penetrating Moscow's air defences.

In particular, they let in light within the blue and red ranges -- the optimal wavelengths for photosynthesis -- but appear to block ultraviolet radiation from penetrating into their shells where it might otherwise damage their DNA.