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 150 days (NC1)  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 150 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.