After an exploratory oil well (IXTOC I) blew out in the Gulf of Mexico in June 1979, three million gallons of oil were estimated to impact the Texas coast, primarily along Padre Island. Booms, either complete or staggered, were placed across the inlets to prevent oil from entering the environmentally sensitive estuaries, including the Laguna Madre. These estuaries are important nesting areas for birds and nursery areas for fish and other marine life. There was concern that subsurface oil of substantial quantities was entering the estuaries under the booms during flood tides. Diving investigations at the booms to observe and quantify the amount of subsurface oil entering the estuaries indicated that between zero and 100 kg of weathered oil was entering the Laguna Madre per day. Except for some small deposits on the shores of the inlet and flats in the estuary, the oil had no obvious impact.