In Reply to: Not much help really, posted by Cat on Thursday, 3. March 2005 at 11:51 Bali Time:
"Goods that must be declared and inspected-----etc-----before being allowed in": Shells
http://www.affa.gov.au/content/publications.cfm?Category=Australian%20Quarantine%20fixand%20Inspection%20Service&ObjectID=91BEA21E-F661-4C28-993E5D87CAB8AF20
"Seashells: You should not import seashells into Australia because of the complex requirements for the export of shells from Australia."
https://www.andersen.af.mil/337asuf/movingtoaustralia/legal.html
As the first website says that we can bring them in, subject to them being declared and inspected etc, I would assume that the second website is referring to "commercial quantities". This is similar to many items which we bring back with no problems in quantities which would be regarded as personal rather than commercial.
Looks like you may have been "got at" for some reason.
There's a shop in our local big shopping centre, Rockingham City, which sells bags of a good assortment of "Indian Ocean" shells for only $2, cheaper than Bali. They are imported from somewhere, I think from India, so there must be ways of legally bringing them in.