Description: Extreme sea level (ESL) events are the phenomena that result in exceptional water level at the coast, which can cause flooding, inundation, and erosion. Recent global scale studies show that relative sea level rise will increase the recurrence of ESL events, by reducing their return period. Also, the compound nature of these events, including the contribution from pluvial, fluvial, and ocean processes, is now understood to affect key processes in estuarine and delta environments. The EOatSEE project (https://eoatsee.eu/), funded by ESA under the Earth Observation Science for Society programmatic line, aims to provide a data-driven description of ESL events as a mean to advance scientific knowledge on this subject matter. It shall foster a community effort, bringing together the EO data provider and the numerical modelling communities, to fully exploit the novel capabilities and synergies offered by the latest advances in EO technology. In this work, a literature review and a collection of needs from the scientific community enabled the identification of current scientific challenges and technical requirements associated with process understanding, predictability and vulnerability & risk assessment of ESL events. Increasing the understanding of the non-linear interactions between oceanic and fluvial processes, and considering coastal morphology response within long-term flooding risk assessments are some examples of the scientific challenges identified, which are to be studied within 9 scientific demonstrators over 6 different coastal regions. Within IUGG2023, a set of preliminary results shall also be presented, as innovative solutions are developed and produced along EOatSEE to address those challenges.