In the harbour of Oslo, local fishermen sell fish and shrimp from their boats in the morning. They come directly from fishing in the Oslo Fjord, and stay in the harbour until today's catch is sold out. Boiled fresh shrimp is the bestseller, but you can also get fish.
The boats come in at 7 in the morning, every day except Sunday, and you find them at Rådhusbrygge 3 (pier number 3 behind City Hall).