When wading a passenger bus through an allowable, shallow flooded road section, what driving technique must be maintained?

1. Engage a low gear (1st or 2nd), maintain steady, uninterrupted throttle, avoid stopping or shifting gears in the water, and exit smoothly
2. Shift into high gear and accelerate aggressively to clear the water in minimum time
3. Depress the clutch repeatedly and pump the accelerator pedal vigorously while in the water
4. Stop in the deepest part of the water to inspect whether water has reached the passenger floorboards