HIMatrix F35 012 programmable controllers are announced as one of the first safety-related designs for SIL 3 subsea applications.
They're suited for use to 4,000 m / 13,123 ft for such tasks as high-pressure monitoring and pipeline pressure isolation. Models comply with ISO/DIS 13628-6 standard. They use low power, can connect with up to several hundred I/O points, plus shock and vibration resistant for -4° to +140°F. usage.