Norwegians have some versions too. The most famous "foul" Norwegian food is lutefisk, or "lye fish", which is cod soaked in lye for six days or more (maybe much more), until it looks like gray jello, but with fish structure to it. Many make fun of lutefisk, saying that it is Norway's way to celebrate old times when people were so poor they had to preserve fish in extreme ways.
Lutefisk however prepared properly is delicious. Especially drizzled with syrup, brown cheese and bacon, with mushy peas on the side. This is coming from an American in Norway, mind you.
A little more extreme is Råkfisk, which is trout that is salted and then fermented ("to ferment" of course means "to allow to rot" -- they are really just the same process) for one to three months. I've heard horror stories about råkfisk and so was reluctant to try, but try I did and while it was not my favorite, it really was not horrible either.