Coastal systems are highly complex, hosting hydrological forcings that span waves to glacial cycles and interlinked ecological, biogeochemical, and geomorphological processes. These systems are also critical – as water supply to billions of people, hosts to valuable habitat, and outsized sequesterers of carbon – and vulnerable – as populations grow, sea level rises, and storms become more intense. Untangling these factors and quantifying feedbacks are essential for coastal system management and prediction of future change, yet the complexity poses a formidable challenge. How do we collect and integrate the data necessary to understand interconnected processes? Can we model these systems, and how do we balance principles of parsimony with process complexity? We present some examples and ideas for observational and modeling approaches to improve understanding and prediction of complex coastal processes in a changing climate.