Wondrous item, uncommon
While you hold the horn you know the direction of the nearest open water within 1 mile of you.
As an action you can sound the horn. Over open water it is heard clearly for 3 miles, through fog, rain, and the noise of a working harbour. Over land it is heard for 300 feet and no farther. A creature that hears it over water knows the exact direction it came from and can hold that direction for 1 hour without sight of sun, star, or shore.
The horn can be sounded as often as you like. It cannot be sounded quietly.
Source: Provenance — The Quist Sale