The swimsuit is the one garment we buy with the express intention of submerging it in water, and water is precisely what it harms. Made, for most of its modern history, from petroleum, it has slipped past scrutiny for years. It is small, seasonal and worn somewhere we associate with pleasure rather than consequence. What has shifted recently is not that anyone has solved this. It is that the swimsuit has become the place where fashion is forced to think about what its products are made of,...