Arriving at your favorite beach only to discover it’s closed because of bacterial contamination can be a bummer. But even worse would be unknowingly swimming in waters polluted with fecal material—a very real possibility, given that current detection methods can require up to 24 hours to obtain results. Now, researchers reporting in the ACS journal Environmental Science & Technology have identified computer models that provide accurate short-term forecasts, or “nowcasts,” of beach water quality.