On the long span there’d have to be two high spots for big boat traffic; on the shorter spans perhaps one would do (better to have two though, one for each direction).
http://en.wikipedia.org/wiki/Giant’s_Causeway#Legend
> According to legend, the columns are the remains of a causeway built by a giant. The story goes that the Irish giant Fionn mac Cumhaill (Finn MacCool), from the Fenian Cycle of Gaelic mythology, was challenged to a fight by the Scottish giant Benandonner. Fionn accepted the challenge and built the causeway across the North Channel so that the two giants could meet. In one version of the story, Fionn defeats Benandonner. In another, Fionn hides from Benandonner when he realises that his foe is much bigger than he. Fionn’s wife, Oonagh, disguises Fionn as a baby and tucks him in a cradle. When Benandonner sees the size of the ‘baby’, he reckons that its father, Fionn, must be a giant among giants. He flees back to Scotland in fright, destroying the causeway behind him so that Fionn could not follow. Across the sea, there are identical basalt columns (a part of the same ancient lava flow) at Fingal’s Cave on the Scottish isle of Staffa, and it is possible that the story was influenced by this.
I'll be able to give you a personal report as (weather permitting) I'll be visiting the Giant's Causeway site next month during a several day stay in Ireland. Looking forward to it with great anticipation!
Very cool..! Thanks for that..!