Apply for and obtain a TWIC card if you do not already have one. Your application will be immediately rejected if you do not submit evidence that you possess a TWIC card. You can apply for the card on the Department of Homeland Security's TWIC site.
Visit the U.S. Coast Guard NMC website to obtain the medical exam form required for your medical examination. Click the merchant mariner credentialing box at the bottom of the page, then click the merchant mariner physical examination form CG-719K PDF about two-thirds of the way down the page.
Complete the medical evaluation report. Provide your name, age, date of birth, social security number and signature in the first section. Sign the release authorization in section two and write the date. Provide a list of medications you take and certified medical conditions you have in sections three and four. A physician completes the visual, hearing and physical exams in sections five, six and seven.
Download form CG-719P from the U.S. Coast Guard NMC website, under the "Applications and Forms" menu. This is the official periodic drug testing form that you must take for a DOT 5 Panel drug test at a Department of Health and Human Services certified lab. A list of certified labs is available on the Coast Guard website.
Obtain documentation of your sea service. You must either present evidence of a minimum of one year of sea service in the past five years, pass an open-book exam covering general subject matter, complete an approved refresher training course or present documentation of employment in operation, repair or construction of sea vessels for a minimum of three years within the past five years.
Download form CG-719B from the Coast Guard's NMC website under "Applications and Forms." This is the application form that lets you apply for your credentialing renewal.
Complete section one of the form, which asks for personal information such as name, date of birth, Social Security number, height, weight and next-of-kin information.
Complete section two. Check the "Merchant Mariner's Document" box and check the "Renewal" box. Under the "State Current or Previous License/Merchant Mariner's Document" box, describe your current credential and place and date of issue.
Complete section three regarding your drug and criminal conviction record. Skip section four, which asks for character references, and sign the mariner's consent section that grants the Coast Guard the authority to access your driving record. Sign the certification section, and sign the oath section in the presence of a Coast Guard official.
Assemble all your documentation and completed forms. Check the Coast Guard NMC website for the appropriate fees related to the merchant mariner position you hold. Write a check or money order for the fee.
Mail the completed application to one of 17 National Maritime Regional Exam Centers throughout the United States. The locations of each center can be found on the U.S. Coast Guard NMC website.