Abstract
Exploration of the solar system has revealed multiple worlds that may host extensive liquid water oceans beneath kilometers of ice. These worlds offer compelling targets in a search for evidence of life beyond Earth. Our understanding of the physics, chemistry, and geology of Earth’s hydrosphere provides essential interpretive context for the initial observations made of these other ocean worlds. As further exploration turns increasingly toward life detection, we can find similar context in our understanding of the biology of Earth’s ocean and leverage the technologies and observing strategies that underlie it.