Visitors must travel here, by boat, as an excursion from a surrounding island, alighting at a small jetty beside the ancient port, now silted up.
Tourists can fly to this location without the aid of a boat.  
mnli hypothesis: Tourists can fly to this location without the aid of a boat.   premise: Visitors must travel here, by boat, as an excursion from a surrounding island, alighting at a small jetty beside the ancient port, now silted up.