The ZED cameras are air calibrated, and as water acts as a lens, you will need to re-calibrate your camera in order to use it underwater.
You can use the ZED Calibration tool if you have a setup that allows you to use a display underwater, otherwise, you must use an external library like OpenCV and a water-resistant chessboard.
Note that the ZED cameras are not water-resistant, so you will need to use a waterproof case that will protect your camera and allow the USB3.0 cable connection.
The ZED2i, ZED X, and ZED X Mini models, even if IP66-rated, is not designed to work fully immersed underwater without a waterproof case.