In their lyrically told follow-up to Flying Deep, Cusolito and Wong delineate various technologies used for underwater exploration, starting at the ocean’s surface before heading deeper via a survey of methods and equipment. A light-brown-skinned child and parent on a snorkel outing start things off, before the narrative moves into free diving, scuba, saturation diving, atmospheric diving suits, and, finally, deep-sea submersibles. Descriptive, often alliterative text sits opposite expository sidebars featuring abridged facts, figures, and dangers for each technology (“Anyone who knows how to swim can learn to snorkel. There isn’t much danger involved”). A collective first-person narration lets readers imagine themselves as explorers (“We’re ocean detectives/ solving the mysteries of the deep”), while realistic, digitally rendered illustrations ferry them to the depths. Largely unlabeled depictions of fascinating underwater creatures, including giant tube worms, should pique interest about what lies below the waves, even as the book’s focus remains solidly on the technologies of exploration. A summarizing spread reveals each technology at various depths; an author’s note, glossary, and resource list conclude. Ages 5–8.