I personally do not work offshore but have several friends that do and a few that are starting out too.
A TWIC card is a good start. https://twicprogram.tsa.dhs.gov. After that, try and get your stcw-95 course out of the way. I believe they do those in Jacksonville and somewhere around New Orleans. Make sure you have ALL the credentials BEFORE you start applying, otherwise they'll just laugh at you and pick from the other 2,000 apps they receive a month.
That's about all the imput I have but others will chime in. Good luck! :thumbsup: