An expendable, self-deploying mooring (XMOOR) for shallow water applications has been developed to address Navy requirements for environmental monitoring. The project has been conducted jointly between the Woods Hole Oceanographic Institution and the Naval Research Laboratory at Stennis, MS. WHOI has taken the lead on the mechanical design of the system while NR has developed the electronics. Eight prototype XMOOR systems have been built. They are designed for water depths between 10 and 100m, for deployments of up to 3-months duration, and for automatic deployment. Their sensor suite includes barometrc pressure, air temperatue, water temperature at up to 25 levels, and conductivity and pressure at up to 3 levels. Data telemetry is accomplished via the Argos DCS and by line-of-sight VH confguration of the data collection program. This report describes the XMOOR mechanical system. The data collection and telemetry systems are described separately in (1) and (2).