A 63-year-old woman presented to an outpatient clinic with an 8-week history of nodules on her arms. She recalled cutting her thumbs while cleaning fish that she had purchased at a seafood market in preparation for a meal, and the lesions began to develop 6 weeks later. She had no fevers. Four weeks before presentation, she had been evaluated at another clinic, where she received treatment with itraconazole for suspected infection with Sporothrix schenckii; no improvement was seen. Physical examination at the current clinic revealed painful pink nodules and ulcerations with a hemorrhagic crust on both arms (Panel A; Panel B is a close-up of the right forearm). A biopsy specimen was obtained and revealed multiple granulomas. Cultures grew Mycobacterium marinum, a nontuberculous mycobacterium that is found in aquatic environments. Infections typically result from exposure to contaminated water when there are breaks in the skin. Itraconazole was stopped, and the patient received treatment with moxifloxacin, rifampin, and clarithromycin for 6 months. She had complete resolution of the infection. At a follow-up visit 1 year later, the nodules had resolved but scarring remained.