dense fog
thick fog
heavy fog

In the heavy fog, how on earth would they find the right one?

There was heavy fog in the morning of the race.

It was like looking at someone in a heavy, dark fog.

Some events are called off when there is heavy fog.

They were once again delayed two hours because of heavy fog.

The heavy fog that night has now become the focus of the investigation, which is expected to take six to nine months.

Heavy fog was particularly hazardous, and could come any time of year.

All of a sudden a heavy fog rose up from the sea.

He was making an instrument approach to the airport in heavy fog.

A heavy fog appeared to be rolling in from the bay.