The fermentation method proceeds while in the can – 'souring' since the Swedes make reference to it – and results in a bulging tin of fermented herring. Or rotten fish, as some (improperly) would say. No matter if you love it or despise it, Swedish surströmming is unquestionably very unforgettable. https://www.youtube.com/watch?v=OS365DWxnKQ