I'd recommend you do a stand alone FAA PPL to hang your FAA SES (Single Engine Sea) rating on, and not a 61.75 licence issued based on a foreign licence. Plenty of comments in PPRuNe about the limitations of 61.75s.
Don't forget that CASA will add a float rating to your Oz licence if you give them money and fill out a form. Bear in mind that Oz considers floats vs floating hull to be separate endorsements, unlike the FAA. If you fly & log both types in the USA then CASA will add both endorsements to your Oz licence. If you only fly the one type that's the only endorsement you'll get.
On the plus side, your Oz float &/or floating hull endorsement, once transferred from your FAA SES, will also be valid for multi engine float &/or floating hull, respectively. Of course you must have a multi endorsement too. Won't matter if the multi was or is done before or after floats. In the FAA world singles & multis, land & sea in any combination are separate licences, requiring four** separate flight tests to obtain privileges across the range. Even more flight tests if you wish move up a licence level later eg PPL --> CPL, or CPL --> ATP.
**Unless you do the tests in an amphibian and land on both ground & water. That halves the total number of tests for single or multi land & sea privileges.
Last edited by Tinstaafl; 7th March 2012 at 15:51.