It's Icelandic shark. I'll quote Rassah on this.
It's poisonous shark that's been burried and left to "ferment" (rot) for months until the poison gets diluted, then hung to dry and rot some more. It tastes like jello that's been made with Clorox bleach. Tastes HORRIBLE! But not as bad as surstroming. Goes well with vodka when frozen though.
I heard they eat this in Norway too (didn't know it was poisonous and a shark though). The person telling me this says it's nearly impossible to keep down. Sounds yummy!