Understanding the ocean is essential to comprehending and protecting this planet on which we live. The Ocean Literacy Guide presents a vision of an ocean-literate society and outlines the knowledge required to be considered ocean literate. The Ocean Literacy Guide describes the 7 most important ideas, or Essential Principles, about the ocean that all people of our water planet should have the opportunity to learn and understand. The Essential Principles and supporting Fundamental Concepts were developed through a community-wide consensus-building process. This effort built on previous work to define ocean literacy, assess what the public knows about the ocean, and redress the lack of ocean-related content in state and national science education standards, instructional materials, and assessments.