George FL Charles Airport (SLU) is just outside of Castries. See the [wiki=d1ef233007d706d71aa6d46642d5f804]Saint Lucia (Get_in)[/wiki] section for more information.
Many visitors will come into Castries on the cruise ships that dock at Point Seraphine.
For details on the ferries that operate from Castries, see the [wiki=d1ef233007d706d71aa6d46642d5f804]Saint Lucia (Get_in)[/wiki] section.
There is actually an anchorage for sailing boats in Castries harbour, although most visitors on sailing boats tend to dock at [url=http://www.igy-rodneybay.com/marina/]Rodney Bay Marina[/url], just outside of [wiki=c09c80907fe9490d7a7bf01c5d8b5346]Gros Islet[/wiki] and then get a bus or taxi in.
These provide a cheap and fun way of getting around:
*1a - to [wiki=c09c80907fe9490d7a7bf01c5d8b5346]Gros Islet[/wiki]
*3f - to [wiki=089cf95e9448832efa3d712a6e693ce6]Soufriere[/wiki].