dense fog
thick fog
heavy fog

She might as well have been standing in a thick fog.

She had been feeling her way through thick fog for three days.

A thick fog came down and it was difficult to see anything.

At once there was a thick fog, and only the red eyes of.

On the day of the race, the weather was poor, with thick fog.

The children were to put to bed as night fell and a thick fog developed.

But a thick fog rose from the ground, and made it very difficult to see the way.

You said we were over it, but I guess the fog's too thick.

I felt as though I'd stepped into a thick fog.

It was thick fog, and one could not see three yards.