This book is an informal introduction to marine biology using life on and near a floating dock in a ocean estuary as examples. We look at large and small animals and plants and follow the development of several species from egg to adult. Who eats who defines food chains in the Dock ecology. A major theme is that diversity and total mass increases as the size of organisms decrease: small is where the action is. Anyone can look under the Dock and see their own special community of organisms. Suggestions for microscopes, plankton nets, use of the Internet, and interacting with professional biologists are described at the end of the book.