The tunnel started a gentle curve to the right and sloped more sharply downward.

The tunnel sloped sharply downward, and the water climbed higher up his body.

Ahead, he discerned low yellow light where the tunnel sloped the right.

The tunnel had sloped downward rather steeply, but now it began to level out.

Now the tunnel was sloping downhill and beginning to curve slightly to the left.

Behind him the tunnel sloped upward, the rut of his passage stopping where he now stood.

The tunnel sloped downward steadily, and there were no steps, so he could run quickly.

The tunnel bent to the left, then sloped downhill where it split into two paths.

He didn't notice that the tunnel was gently sloping uphill, had been for sometime.

Probing with the flashlight, I saw that the tunnel sloped and gradually curved away to the left, out of sight.