Tangaroa Blue coordinates clean-ups across Australia and, more importantly, runs the Australian Marine Debris Initiative (AMDI), the national database of what is found where, which feeds Great Barrier Reef water-quality report cards and source-reduction plans. Donations fund the database, ghost-net and microplastics work and volunteer coordination.
Its donate page states it is an Australian registered charity with deductible gift recipient (DGR) status and approved for US tax-deductible gifts through Charities Aid Foundation (CAF) America. Honest caveat: the Australian Business Number and Australian Charities and Not-for-profits Commission (ACNC) listing are not printed on the site, so check the ACNC register before a large gift.
Give data instead: any clean-up can be logged in the AMDI database (app at amdi.tangaroablue.org/ login required; email Tangaroa Blue to be set up or to join a coordinated event). Standardised counting matters more than volume.
How to start: tangaroablue.org/donate/