Wondrous item, rare
Three levers, one key. The lid can be raised only while the creature holding the key is afloat: aboard a vessel, a raft, a plank, a hide of ice, anything that water is holding up. Standing in water with your feet on a bottom is not afloat, and neither is a boat aground. Ashore, the key turns and the lid does not.
While the lid is down the box cannot be forced, cut, burned, drilled, or unhinged (AC 19, 80 hit points, resistance to all damage), and no spell or sense reveals what is inside it, how heavy the contents are, or whether there are any. It weighs 74 pounds full or empty.
The well beneath the tray holds 1 cubic foot and 60 pounds. What is put into the well does not wet, does not mould, and does not take salt.
No instance of this box being opened on dry land is of record with this house, with the office of the Waterbailiff, or with the owner.
Source: Provenance — The Quist Sale