COASTAL Implementation Act of 2018 This bill amends the Omnibus Public Land Management Act of 2009 to revise the authority of the National Oceanic and Atmospheric Administration, including to authorize (1) the deployment of sensors to enhance data collection in coastal states that are at highest risk of experiencing geophysical events, and (2) post-storm assessments for each coastal state that suffers indeterminate loses from a storm. The bill amends the National Flood Insurance Act of 1968 to require the Federal Emergency Management Agency to publish for comment in the Federal Register a standard formula (COASTAL Formula) to determine and allocate wind losses and flood losses for claims involving indeterminate losses.