Underwater technology is advancing with the development of instruments capable of measuring continuous data for longer durations for diversified ocean data collection. A bottom pressure recorder is deployed on the seabed to measure the water level for tsunami early
warning, thus playing a critical role in saving lives. Recently, many countries have installed their warning systems. Here, we report an unusual corrosion of such an instrument deployed in the deep sea (3,250 m) in the Bay of Bengal, which led to severe damage of the instrument. This paper
reports for the first time on the investigation and possible causes for this unusual corrosion of an instrument made from highly marine corrosion-resistant aluminum alloy and duplex stainless steel material.