i would like to travel to Australia via ship from America, can you do that?

Here's a cruise that leaves in about 10 days that does exactly what you want.:

http://www.princess.com/pb/itineraryDetails.do?subnav=true&voyageCode=S733&to urCode=&resType=C&noOfPax=2&shipId=SP&shipName=Sun +Princess&co=US&productCode=PTP300&departureDate=S ep+23%2C+2007&productDesc=Hawaii%2C+Tahiti+%26+Sou th+Pacific+-+Seattle+to+Sydney

It is on Princess and though the time for this one is short, it is likely to be run again next year, if not later this year. Then this cruise is run in reverse next year:

http://www.princess.com/pb/priceDetails.do?voyageCode=H810&tourCode=&date=&no OfPax=2&resType=C&definition_name=

And then this is a Holland America cruise to Australia next year:

http://www.hollandamerica.com/dest/itinerary.do?selectedItin=20080925:V855B:PS8029&de st=P

yes there are cruises there. Cunard, Princess, Holland America. alot of these cruise companies have even around the world cruises.
best wishes.