Janell Gregerson’s toenails are painted hot pink, a tropical color that evokes the joys of lounging by the water, margarita in hand. But as the single mother of four walks out her back door in Cedar Park, a suburb northwest of Austin, to “show off” her swimming pool—which she installed in 2021 for $120,000, after saving for six years—it’s clear she hasn’t been enjoying much aquatic R&R. After less than three years of use, her pool has become a gaping, dangerous hole, its plaster crisscrossed by dozens of cracks. In the deep end, a nine-foot drop from where Gregerson stands, hundreds of mosquito larvae wriggle through a murky green pond fed by two months’ worth of rain. Gregerson says red wasps like to congregate at the…