Underwater Secrets in Fallout 4 (Treasure #6)
Location: Mahkra Fishpacking
INFO: (Make sure you have the perk that lets you breathe under water or you won’t make it there. It’s called Aquaboy and can be found in the endurance perk section)
Make your way to Mahkra Fishpacking, which is in the top right corner of the map. From the main entrance, take a right and walk to the shore to find the message in a bottle with your loot objective. Like before, swim to the marker, dive down and look for the steamer trunk and a small bathtub next to it.