Carbonate sediments are the sole indigenous source of aggregate for infrastructure development on many Pacific islands, and their importance has increased markedly since the middle of the last century. Biogenic gravel and sand are extracted in many places by dredging of shallow lagoons and by the mining of beach deposits. As demand increases, environmental and other problems caused by unrenewable, and thus unsustainable, and/or inappropriate extraction of this limited resource have grown. Majuro Atoll in the Marshall Islands exhibits many of the problems that are widespread in the Pacific. There is now concern on this atoll about damage to the coastline and the largely uncontrolled nature of aggregate extraction, linked to pressure to increase the habitable space by coastal reclamation and leading to the need for discourse among land owners, developers, and government agencies. The lagoon is large and well suited to study by high-resolution multibeam swath mapping, which has allowed three-dimensional imaging of aggregate deposits and dredge scars and pits. Thus, the technique is valuable both for rapid and accurate surveying and, used in conjunction with satellite imagery, as a means of providing to stakeholders colored images of past damage and areas of future interest.