Book excerpt: Life in the estuary is always changing. Ocean tides of salt water flow in and out of the estuary and mix with the fresh water that flows from rivers and streams. The animals that swim or wade in the waters or make the mudflats their homes must have physical or social adaptations that allow them to live in the salty mix. In this book, readers in grades 3-5 will discover how and why animals survive and thrive in these sheltered biomes. This NGSS-aligned series is packed with interesting facts and vivid photos that introduce readers to a variety of land and water animals. Each book includes a glossary, comprehension questions, and an activity for home or the classroom.