He pointed out the rocks hidden in the deeps.

Here an Italian liner that was going to Buenos Ayres had been lost....

A little further on, a swift four-masted sailboat had run aground, losing its cargo....

He could tell by the fraction of an inch the amount of water permissible between the treacherous rocks and the keel of his boat.
He usually sought the roughest waters by preference, but they were in the danger-zone of the Mediterranean where the German submarines were lying in wait for the French and English convoys navigating in the shelter of the Spanish coast.

The obstacles of the submerged coast were for him now the best defense against invisible attacks.
Behind him, the Ferrarian promontory was growing more and more shadowy, becoming a mere blur on the horizon.