Caught him! When he saw us passing the bridge he flew upstreams beneath us. I'm not a very quick photographer, but was lucky this time.
Strömstare - Cinclus cinclus - is 'dipper' (!). He migrates south, but not very far; this one is probably from northern Scandinavia. We see him often in winter here by the river.
Ström is 'stream' and stare is 'starling', but he is not much like a starling, black but with white breast (I see in my bird guide that English 'dippers' are brown instead of black).
Perhaps you have heard the old tale about svalor - 'swallows' and 'house martins' - hibernating under water. It is said that people who saw strömstarar diving into the water can have believed they were swallows.
(New post about strömstare added February 2012: http://svenska.iedior.se/#post146..)