If you dive, snorkel, or photograph marine life in Southeast Asia and want to accurately identify reef fishes you encounter underwater, this book is designed for you. This is a photographic reef fish identification field guide for the Coral Triangle —the marine region that includes the waters of Indonesia, Papua New Guinea, the Philippines, Malaysia, Timor-Leste, and the Solomon Islands . It helps divers and underwater photographers identify fishes as they actually appear in the wild , not as illustrations or preserved specimens. The guide includes over 1,500 species of reef and coastal bony fishes that can be encountered and photographed within depths accessible to recreational diving. All species are illustrated using photographs taken in natural conditions, without traps, anesthetics, or chemicals harmful to coral reef ecosystems and their inhabitants. Photographs document natural coloration and real underwater appearance. Where available, images show color variations , sexual dimorphism , and different life stages , including juvenile forms—features that are critical for reliable identification and are often missing from traditional guides. Many species included in this book have never appeared in popular field guides. Some were only recently described (2015–2025) , while others were previously known primarily from preserved specimens in laboratory or museum collections and documented mainly through photographs of dead material. Several species included here are still awaiting formal scientific description. Taxonomy follows the latest scientific consensus and is fully synchronized with updates from Eschmeyer’s Catalog of Fishes , ensuring that species names, family assignments, and classifications reflect current ichthyological research—an important advantage for readers who rely on accurate and up-to-date information. Each species entry is presented in a clear, field-oriented format, including the common name, scientific name, family, geographic distribution, maximum size, and key identification features. An extensive photo index at the beginning of the book allows quick navigation between major fish groups, making the guide practical even for readers who are not yet familiar with scientific names. The layout of 10 photographs per page enables efficient visual comparison of similar species, significantly speeding up the identification process. Designed for use both in the field and as a reference, this guide emphasizes what divers actually see underwater : live reef fishes in their natural habitats and under natural lighting conditions.