Answer
This is a critical, life-threatening stability failure. As Chief Engineer, take the following systematic actions:
Engine Room Safeguarding:
Verify the running machinery layout. Main engines and diesel generators may trip due to low oil pressure caused by the severe list shifting oil away from pump suctions in the deep sumps.
Switch over to low-aspect or high-side/low-side sea suctions as appropriate to prevent loss of cooling water. Monitor main sump levels continuously.
Identify the Cause: Coordinate with the bridge to determine if the list is due to negative stability, cargo shift, or accidental flooding/asymmetrical tank equalization.
Engineering Interventions (Corrective Actions):
If due to Cargo Shift/Flooding: Ballast or de-ballast corresponding tanks on the opposite (high) side only under direct authorization of the Master after validating the stress figures on the Loadicator.
If due to Angle of Lol (Negative GM): NEVER start by ballasting the high side. This will cause the vessel to roll violently to the opposite side and likely capsize. First, eliminate the Free Surface Effect (FSE) by topping up slack tanks or completely draining them, starting with the lowest tanks. Then, ballast the low side first to lower the center of gravity ($G$), before correcting the list.