Beaches Environmental Assessment and Coastal Health Act of 2021 or the BEACH Act of 2021 This bill reauthorizes through FY2026 and expands a program that awards grants to state and local governments to monitor the water quality at beaches and notify the public when water is not safe for recreational activities. The bill expands the program to allow the Environmental Protection Agency to award grants for researching and identifying specific sources of contamination at certain coastal recreation waters and taking actions to mitigate those sources.