The best yet of Ryder's ``Just for a Day'' books: ``you'' are a boy whose imagination takes you from a rainswept beach to being a humpback whale, exulting in the experience of ``gliding up and down between...sea and sky.'' Ryder's evocative text dwells on the joy of movement and also considers the pod, a new calf, and its mother, and the whales' mysterious warm-water song. Rothman's whitecapped underwater vistas are gorgeous, from rich purple depths to light-drenched apple-green surface. An author's note extends the informational value. A fine celebration of this appealing creature. (Picture book. 4-10)
