PADI instructor Ken Davis travels to the Florida Keys
2-3 times per year. He purchased a padded Akona gear
bag, but reports that “My new dive bag has holes, broken
zippers, grease, and looks 10 years old.” Although
his gear has escaped destruction, Davis says, “In the
future, I plan to mail my mask, fins, and computer to
the dive shop ahead of time and will take a pass at letting
the airlines trash my expensive dive gear.”
Besides the post office, several companies pick up
  at your door and deliver directly to many destinations.
  Rates and speed of service vary. Frommer’s has found
  that FedEx is the low-cost domestic provider for fiveday
  ground service ($33.80 to ship a 54-pound bag
  from New York to Seattle). For faster deliveries, a competitor
  called Luggage Free was cheaper.  
International rates are sky high. FedEx quoted
  almost $600 to deliver a 44-lb. bag from the San
  Francisco Bay Area to Belize City in three business days.
  DHL will ship the same bag to Australia for $400. (Get
  quotes for any destination at www.dhl.com). Rates drop dramatically if you can ship weeks in advance
Shipped luggage can be insured cheaply. You’ll
  need to provide customs declarations, including your
  itinerary, passport number, and an inventory of the contents.
  Some countries charge duties and taxes.  
So while the cost of shipping internationally is
  extreme, international carriers are charging more for
  extra bags. And if you’re off to Australia and you left
  your camera gear at home, a timely call from the airport
  to a friend or spouse might still get the bag to you
  in time to not ruin your diving. Or, if you’re returning
  home with suitcases of artifacts, shipping by slow boat
  may be much less expensive than paying for excess luggage.
  A hotel concierge can find a shipper for you.  
A few unique shippers: Luggage Express
  (www.usxpluggageexpress.com or 866-744-7224);
  Luggage Free (www.luggagefree.com or 800-361-6871)
  and Virtual Bellhop at www.virtualbellhop.com or
  877-235-5467.