Book excerpt: Throughout history, people have always explored new frontiers. Adventure, fame, and scientific discovery have all driven humans to forge into the unknown. This title examines exploration under the sea. Easy-to-read, engaging text takes readers to deep ocean trenches, examines the explorers who journeyed to these strange, fascinating areas, and traces the development of the technology and techniques that made this exploration possible. Well-placed sidebars, vivid photos, helpful maps, and a glossary enhance readers' understanding of the topic. Additional features include a table of contents, a selected bibliography, source notes, and an index, plus a timeline and essential facts. Aligned to Common Core Standards and correlated to state standards. Essential Library is an imprint of Abdo Publishing, a division of ABDO.