A groundbreaking study published in *Nature* has uncovered a significant underestimation in baseline coastal water heights, leading to a stark revision of the number of people globally at risk from rising sea levels. The study reveals that approximately 90% of prior research underestimated these crucial measurements by an average of 1 foot (30 centimeters). This discrepancy is particularly acute in the Global South, Pacific, and Southeast Asia, while less pronounced in Europe and Atlantic regions.