Go towards the Ruins of the Ancient in the River towards the north, and before the gate to the big Ancient, you'll be able to find the map. You'll gain 5000 Hacksilver, 5 Soft Svartalfheim Steel, an Oblivion Stone and an enchantment. This one is super easy, and only takes a few minutes. Go over and up the well under front underneath the house to the front of the Witch's house, go towards the massive Turtle and you'll be able to find the digging spot near the Turtle's Head.
There, you can blow up a barrier with the arrows and go into the now open room to obtain the map. Then, you'll be able to see the light arrows towards a Nornir Chest underneath the Witch's Cave. In the Witch's House, ensure you're at a point in the story where you have unlocked the Shock Arrows and once again let the World Serpent lower the water again. a Legendary Enchantment, a Glacial Catalyst and 2 Solid Svartalfheim Steel. Underneath the face before a staircase, you'll find the digging spot to get 6000 Hacksilver. Remember that huge ominous face on the side of the Mountain? Yeah, go there again. You might want to undertake the Fafnir Sidequest, which will lead you to the greedy Dwarf's Storeroom, in the middle of the rotating temple, you'll find the map, this one is pretty hard to miss, and easy to pick up when you're doing the quest. You should be able to find the captain's booty in the Isle of Death- Towards the south, you'll be able to find a ship behind a rock, go inside the ship and up towards the top to find the treasure, which is an Etched Crest of Courage, 30 Aegir's Gold and 10000 Hacksilver. The Boat Captain's Key Treasure Location: If you've lowered the water a second time, you will need to dock at the Stone Falls and climb until you see the two gates and hang left. There you will find a map in a puddle near a broken bridge in between two rocks next to two gates. Near the Stone Falls to the northeast on the Lake of Nine, just north-east of Buri's Storeroom.
Watch on YouTube 8 Things We Wished We Knew Before Playing God of War Treasure Map 1: The Boat Captain's Key