Sea Witches

In haunting haiku a grandmother admonishes her grandson to heed an ancient superstition: ``When you're done eating, / give your eggshells a beating! / Never leave them whole!'' The old woman recounts a mysterious tale of sea witches who alchemize discarded eggshells into ships and prey on unsuspecting sailors: ``The witch- storm attacks-- / Savage winds and lashing rain / From lightning-streaked clouds.'' With their shaggy, raven tresses and pale bony limbs, Gal's ( The Enchanted Tapestry ; The Willow Maiden ) cackling hags form an eerie underwater coven. Robertson's debut book uses straightforward language to achieve striking images; adults may well utilize her text to introduce the haiku form to young writers. In a somewhat overdesigned format, however, a static border illustration framing every spread adds little, and may distract the reader from the ocean's rage and thrash. Still, text and paintings blend stylishly to form a chilling tale. Ages 4-8. (Oct.)