A girdle of smoke curled itself around their double smokestacks.

Their prows when not hidden were expelling cascades of foam, sometimes even showing the dripping forefoot of the keel.
At night time they would all travel with few lights, simple lanterns at the prow, as warning to the one just ahead, and another one at the stern, to point out the route to the ship following.

These faint lights could scarcely be seen.

Oftentimes the helmsman would suddenly have to turn his course and demand slackened speed behind, seeing the silhouette of the boat ahead looming up in the darkness.

A few moments of carelessness and it would come in on the prow with a deadly ram.
Upon slowing down, the captain always looked behind uneasily, fearing in turn to collide with his following ship.
They were all thinking about the invisible submarines.