Swai is a mild, farmed freshwater whitefish (Pangasius hypophthalmus, also sold as tra or striped catfish) native to the Mekong River basin in Vietnam, Cambodia, and Thailand. It has a delicate, low-fat texture and a subtle flavor often compared to tilapia or cod, and is commonly sold as a cheaper substitute for those fish. Most swai on the market is pond- or cage-farmed in Vietnam and exported widely, including to the United States. It takes well to baking, grilling, pan-frying, poaching, and steaming, and appears in Asian curries and fish cakes as well as Western-style fish tacos, sandwiches, and chowders. Swai farming has drawn scrutiny over antibiotic use and water pollution, and the fish has at times been mislabeled or substituted for pricier whitefish, so it's worth checking sourcing before buying.