If the heavily traveled route between Italy and N. Africa actually went over this 'treacherous reef' that is near the surface, I'd expect to find a lot more ships than five.
Sailors aren't stupid and don't put their ships as risk unnecesarily. My guess is that these ships probably strayed over the reef by accident or were driven by storms.
"Who's been reading Patrick O'Brian?! " -- Alkhin
here's a :'D even though I don't know who that is. :')
"Sailors aren't stupid and don't put their ships as risk unnecesarily. My guess is that these ships probably strayed over the reef by accident or were driven by storms." -- wildbill
Wholeheartedly agree! Hugging the coastline is something else they would have avoided, sailing straight in and out of ports, unless they knew that coastline like the backs of their hands (and in the case of the seas by Sicily, probably not then either).