Compass

The spell requires is a brass bowl filled with water, with a circle of cork set afloat in it. Atop the cork is affixed a long iron pin or needle, painted red on the pointing end. When the spell is cast, the cork stays centered in the bowl and rotates until the pointer aims in the direction defined by the caster.

This pointer always points in a direction defined by the caster. This is often a map direction, but it can be more abstract: the compass may always point to their home port, or their destination, for example. The caster can choose only a familiar direction, such as a place he has seen or a direction of which he is certain.

In calm weather the compass is easy to read, but in rough waters the float bobs about enough that reading properly the compass requires a successful Intelligence ability check; if the check fails, the reading is off by 20° to 180°. If all the water is drained from the bowl or the cork is removed, the spell is broken. For this reason, the compass often is covered with glass to keep water and float in place.