This event is called Transsegre and it takes place in Balaguer, Spain. Looks pretty fun and the water seems a lot cleaner than in Keravajoki..
Unlike the Finnish Kaljakellunta however, this event is heavily regulated. All vessels are inspected before the 2 day festival and their number is limited to 300. Life jackets are compulsory and all vessels must have registration numbers. According to their website alcohol is prohibited.. now where is the fun in that :D?