Ajai wrote: Wiki says causeway, a raised road, 'ultimately derives from the Latin calyx, meaning heel' because the path was trampled down which ties in nicely with Hermes and lame heroes. However this kind of causeway, formerly causey or cauce, is underwater and out of sight, to be navigated with caution.
A causeway is an artificial strand or strait. It allows ships to pass at high tide and people to cross at low tide. For a price presumably.