The floating, grabbing digger machine

I saw this green digger make its way down to the Thames and thought it had got the tides wrong.

It was heading downriver where the gravel was being levelled at a dock used for large boats carrying aggregates. I expected it to wait until low water and then make its way along the dry edge of the shoreline, but it rushed into the deep water.

Turned out it floats and can drag its way along using its arm as a forward punting pole, like something out of a Top Gear special.

These kayakers seemed pretty gob-smacked (to use the technical word).