This is a photo of the Dar Młodzieży, (more photos and a description in Dutch) (Wikipedia page in English) during Sail-in, 19 August 2010 between IJmuiden and Amsterdam, somewhere on the 'Noordzeekanaal'. That is the Netherlands.
In the photo you see the flag of the event, as flown from the Margeja, which was the boat I was a passenger on. Also in the picture a few of the other boats in the canal.
In this newspaper page you can see an area view of the event, with an other ship central. The water is crazily busy and the city of Amsterdam gets overcrowded during the (free to visit) event.