Treasures of all kinds await you as you journey through Assassin’s Creed Valhalla, including the treasure at the bottom of a river.
Such is the case with The Last Flight of the Gydan Sparrow world event that you can find in Lunden. If you go to the city’s docks, near the southeastern corner, you will find three people there having a conversation about a recent shipwreck.
Speaking with the woman there, Eivor will offer to dive down and investigate the goods that were on the ship when it sank, including a necklace. She will suggest you dive in and see what you can recover, and Eivor will agree, of course.
You can see the shipwreck right off the dock by the mast sticking out of the water and the fish jumping around it. Using your Odin’s Vision will show you a couple of things of wealth down in the water, so hop in.
The ship will have two chests in it, one of which will give you a message in a bottle. Take this back to the woman, and she will say that the note mentions the necklace being hidden in a cow’s stomach. Given that the ship was in water, a cow eating it wouldn’t make much sense.
But her last words will mention having to “fish” for the treasure, which is the clue you need. Go to the dock’s end and cast your Fishing Line into the water, near a fish. The first fish you catch will have the necklace.
Bring it back to the three people, and they will allow you to choose if you keep the necklace or not. Either one will end the quest, but keeping it will allow you to sell the necklace to a merchant for some extra Silver. It’s up to you.