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.