A VTS operator is monitoring a vessel that has reported a main engine failure and is drifting towards a sensitive marine area. Which of the following actions, if available to the vessel's master, represents a critical last-resort measure to arrest the vessel's drift?

1. Deploying the vessel's anchors.
2. Making a 'Pan-Pan' call on VHF Channel 16.
3. Displaying the 'Not Under Command' lights and shapes.
4. Requesting a tug from the nearest port.