Rainbow (Prosperity) is a saltwater beach in St. Croix Island County, U.S. Virgin Islands. Across 27 bacteria samples collected between 2021 and 2022 at nearby monitoring stations, it earns a Beach Safety Grade of D — Poor.
About 19% of samples at Rainbow (Prosperity) exceeded the EPA Beach Action Value of 104 CFU/100 mL for Enterococcus — the threshold at which water managers typically post a swimming advisory. In practice that means the safe-swimming limit was frequently crossed here over the monitored period. Bacteria samples frequently exceed the safe-swimming threshold; swimming advisories are common here.
Read this grade as directional rather than settled: it draws on a single monitoring station, rests on only 27 samples and has no results reported since 2022. That is enough to classify how the water has behaved, but not enough to separate this beach from another a grade away — a beach graded from thousands of samples at several stations is a firmer read. As more results are reported, the grade may shift.
Rainbow (Prosperity) was not under a swimming advisory in the most recent EPA snapshot. Conditions can change quickly after heavy rain or high runoff, so it's still worth checking the current advisory the day you go.