Farber (When It Snowed That Night, 1993, etc.) begins her sleeptime fantasy quietly: ``Night is dark,/Night is deep,/I swim an ocean in my sleep.'' In Savadier's whimsical ink and gouache illustrations, a small boy in red-striped pajamas swims through an imaginative underwater world. He plays with a mermaid, rides on a whale, and dances to the rhythm of a clamshell castanet. Finally he rises out of the water, clinging to a huge red balloon, for ``now it's time/to step once more/wakened on the morning shore.'' Especially appealing is the final picture of the sleep-tousled, bemused boy, sitting on a bed strewn with sand and seashells. There are nice moments in the text as well, but sometimes the perceptions of the author intrude, resulting in a narrative that wavers between the child's point of view and a more sophisticated perspective. (Picture book. 4-8)