If you've been there and done that, you can simply fast travel to the Tu Ka» loh Shrine at the heart of the labyrinth and jump
down a hole to find the labyrinth's basement, where you'll find the
chest to the north of the room
near the centre — watch out though, there are Guardians lying in wait.
On big ships, try putting your
chests behind the staircases
down to the holds, on the balcony behind the captain's quarters, or
near the clothing, equipment and vanity
chests on the mid-deck, where they might blend in.