We had a monitoring unit in a heavy aluminum box on a buoy a couple km off Biscay (the HARSHLab, heh...) that lasted half a year, until the stainless bolts cor

We had a monitoring unit in a heavy aluminum box on a buoy a couple km off Biscay (the HARSHLab, heh...) that lasted half a year, until the stainless bolts corroded against the aluminum and the lid flew right off. Polycarbonate boxes have worked better for us.