A versatile author at her best, with an introduction to an aquarium she bases on several modern installations in the US. With his brother and sister, the narrator explores a full range of exhibits—coral reef, deep sea, river, tidal, etc.—lucidly describing what he sees and including plenty of concrete detail, well chosen to exemplify the variety and adaptations of aquatic life. In the large, cheerful illustrations, action-filled spreads are varied with portrait vignettes, and underwater scenes with the visitors' enthusiastic responses. Unobtrusive labels for many species and a fervent, sensible environmental plea round out an unusually attractive and useful offering. (Nonfiction/Picture book. 4-8)