While exploring the Island of Waford in One Piece Odyssey, you’re bound to find loads of treasures along the way. One such category of treasure is the Locked Chest which contains resources vital to your survival on the island provided you have a chest key to open them with. Below is a guide on where you can find the locked chests in Marineford. Opening all of them rewards you with the Treasure Hunter trophy/achievement. Please note that you will have to complete the Grand Line Quiz questline in order to receive the key needed to open the chests. You can find details on those quests here.
Marineford City Area
Town Outskirts
The chest can be found next to a building near some crates and barrels on the right side of the road heading north from the save point.