AXYS has provided sub-surface environmental monitoring systems for a variety of challenging marine environments. With an array of sensors, including temperature, dissolved oxygen, and water chemistry, data can be transmitted to a surface buoy for processing using an acoustic modem or an inductive mooring line. Two-way communication capabilities allow remote system management, including configuration and diagnostics of both the buoy and the mooring components. Sub-surface moorings are easily recovered using acoustic releases, which can be triggered at any time, allowing the instrumentation to float to the top and leaving the anchor on the seabed.