Sea Service Letter or AMSA 

Coxswain Task Book

If you wish to claim a reduction in sea service requirements then complete an

AMSA Coxswain Task Book

When making an application to the Australian Maritime Safety Authority (AMSA) for a Certificate of Competency as a Coxswain they will require, in addition to your course certificates, AMPA, and application documents:
Evidence of sea service experience.
Providing evidence of sea service experience can be done in one of two ways:
Firstly if you have the required 240 days (NC1) or 60 days (NC2) of sea time then you can provide a letter or Statutory Declaration (a legal document available at any newsagent) stating your experience. 

OR

For a COX NC1 Certificate the 240 days of sea time (Can be 100% recreational or a combination of recreation and/or commercial) is reduced to 30 days commercial experience with a completed AMSA Coxswain Task Book.

For a COX NC2 Certificate the 60 days of sea time (Can be 100% recreational) is reduced to 7 days experience with a completed AMSA Coxswain Task Book.