If you have a ship assignment that is based around Australia, you will need either 1 or both of the visas below.
The Maritime Visa (subclass988) allows you to enter Australia by sea as a Crew Member.
Maritime Visa details: http://www.border.gov.au/Trav/Visa-1/988-
To be allowed access into Australia by air please apply for the below:
eVisitor details: http://www.border.gov.au/Trav/Visa-1/651-