Abstract The ocean plays a key role in regulating the climate as well as supporting diverse ecosystems. Technology is the key for the sustained and precise in-situ spatio-temporal measurements of the physical, biological, biogeochemical, and near-atmospheric meteorological parameters essential for carrying out effective assessments of the status, variability, and change in the ocean ecosystems and for creating policies at the right time. The United Nations Decade of Ocean Science for Sustainable Development 2021‐2030 provides a timeframe to build a comprehensive, sustainable, and data-based informed decision-making global ocean observing system. This demands global-scale investigations, trans-disciplinary science, and mechanisms to integrate and distribute data that otherwise would appear to be disparate. The essential ocean variables (EOVs) conceptualized by the Global Ocean Observing System (GOOS) of UNESCO's Intergovernmental Oceanographic Commission guide observation of the ocean. In order to achieve the goal of UN Decade envisaged and to have an Earth System approach under the World Meteorological Organization reforms, it is imperative to address globally and nationally relevant indicators and assessments, which require increased sharing of data and analytical methods, sustained long-term and large-scale observations, and resources dedicated to these tasks. Technology for observing the ocean is important, which is not addressed in detail in the recent past. In this paper we provide a comprehensive overview of Sensor versus Essential Ocean Variable from our experience in sustained 25 years of moored ocean observation network and collaborating with institutions and experts in the United States and GOOS. An attempt has been made to furnish an overview for any group or nation to start or sustain an observation network using EOVs with guiding principles of Findable, Accessible, Interoperable, Reusable data that is targeted to deliver essential information needed for sustainable development and protecting ocean health.