The United States Army Corps of Engineers (Army Corps) maintained shipping channels in and outside of the Boston Harbor. The Army Corps periodically conducted surveys of the channels to determine their actual depths. The Army Corps’s manual detailed that the Army Corps’s province was engineering and construction activity, not the preparation of precise nautical charts. The National Oceanic and Atmospheric Administration (NOAA) was the federal agency whose province was precise hydrographic mapping and production of nautical charts. The Army Corps, following its own manual, employed surveying procedures that were less exacting than those the NOAA employed in conducting surveys. No regulation precluded the NOAA, however, from using information from surveys that did not conform to NOAA standards in the creation of its own nautical maps and charts. Similarly, no regulation required the Army Corps to perform its surveys to the more exacting standards of the NOAA, even if the Army Corps knew that the NOAA would use the surveys’ results. The NOAA published a nautical chart of the Boston Harbor using, in part, results of the Army Corps’s survey. The pilot of a vessel owned by Limar Shipping Ltd. (Limar) (plaintiff) was using the chart as he approached the Boston Harbor. The chart understated the harbor’s depth, and the ship grounded, causing approximately $800,000 in damage. Limar sued the United States (defendant) under the Suits in Admiralty Act in district court. The district court granted summary judgment in favor of the United States, finding that the Army Corps’s and the NOAA’s conduct fell under the act’s discretionary-function exemption to the act’s waiver of sovereign immunity. Limar appealed.