Depth Warning

By means of this spell, a caster aboard a ship can alert the crew to a sudden change in water depth. This is particularly valuable if the change is the result of a reef, shoal, or underwater behemoth that may threaten the ship. The spell can detect any obstacle at least as large as the vessel's own keel.

When casting the spell, the wizard selects the depth that he wishes to monitor, up to 10 feet per experience level. The caster next decides whether to center the spell directly below the ship's bow, or 40 yards in front of the bow. (If the ship changes its heading, "in front" changes accordingly.)

The spell creates an intangible and invisible pole, which probes straight down to the desired depth, at the location chosen. Whenever it detects a large obstacle, a small voice magically alerts the caster, reporting the depth of the water in his ear. Only the caster can hear this voice, and while it rouses him from an ordinary slumber, it cannot negate the effects of magical slumber or unconsciousness, nor does it interrupt other spellcasting. Ordinary noise, even the sound of the sea, does not negate this small voice, nor do magical or natural deafness.

Once it begins, the magical voice continues to provide "readings" of the obstacle's depth in ten-foot increments. Each time the depth changes by 10 feet, the small voice records the change. If the depth increases to a level beyond that monitored by the spell, the small voice notes this fact then remains silent until the ship is again endangered. This spell does not provide physical protection against collision with large objects, only notification that they exist. A large, live object (such as a whale) can activate this spell, provided the object is larger than the protected ship. Any non-living object capable of damaging the ship is also noted

The material component of this spell is a clear glass bead, which is crushed in the process of casting.

Notes: Common in Arabian settings; virtually unknown elsewhere.