Between January 1, 2018, and April 25, 2021, over 800 fishing vessels conducted nearly 900,000 hours of apparent fishing within 20 nautical miles of the invisible border between Argentina’s national waters and the high seas. During this three-and-a-half-year period, there were over 6,000 instances in which these fishing vessels appeared to go “dark” by potentially disabling their electronic tracking devices, known as Automatic Identification Systems (AIS). These vessels’ activities were hidden for over 600,000 hours. Nearly 66% of the “dark” vessels were Chinese-flagged squid jiggers (i.e., vessels with bright lights and hooks designed to catch squid). Despite having a smaller fleet, Spanish trawlers (i.e., vessels that tow heavy nets to catch species like Argentine hake and red shrimp) went “dark” more than three times as often as Chinese vessels. Illegal, unreported, and unregulated (IUU) fishing thrives out of sight and undermines efforts to responsibly manage and protect our oceans. Disabling AIS hides fishing vessel locations from public view and could mask potentially illegal behavior, such as crossing into Argentina’s EEZ to fish.