Pachygrapsus transversus, the Mottled shore crab (juvenile);
Flagler county, Florida (01 July 2019).
Learn more about this species at iNaturalist.org.
NOTE: Identification should be considered tentative at best. Though I’m confident this is a Pachygrapsus, I’m not entirely sure of the species. It should be the Mottled shore crab (P. transversus), but it could be another non-native species moving into the region.