One of the problems of living on canals is that eventually dirt and rubbish accumulates at the bottom, and needs to be removed. Currently there’s a dredger working on Brouwersgracht.
The blue woonboot (houseboat) you can see has been moved out of it’s normal spot while the dredger works behind it. Tough luck if they people forgot their wallets when they left in the morning.
When I cam back in the evening the houseboat was back in its place and the dredger had moved on.