"AB" is short for Able Bodied Seaman. It is an unlicensed rating above Ordinary Seaman. It is a tough job market out there on US flag vessels. There are jobs in the "oil patch", but even those can be hard to get. Most deep water supply, construction and drilling vessels are "Dynamically Positioned" (DP) and there is further training above Third Mate to get a DP Operator's job.
This turn was happening back when I got out of school. I spent a year shipping out of the MEBA hall in San Francisco and got VERY lucky to land 90 days on a container ship, transit to the East Coast and then a northern Europe run. Nothing else came up the next year, so in August, I took a job with Crowley running tugs from Louisiana to the Caribbean. I moved to ITB/ATBs from there.
I do know that there are a lot of ITB/ATBs being built (Integrated Tug Barge/Articulated Tug Barge) to meet Jones Act intercoastal trade and double hull requirements. I would imagine that the jobs are pretty competitive, though. As much as I liked going to sea, I am happy in my mostly shoreside work.
My last sailing gig was not what I wanted, but I took it since the good Chief Engineer's berth that I had was sold out from under me after four years. Without warning. It made coming ashore some 20 years ago somewhat easier. In an unusual turn, my new shore side job actually paid more that what my last sailing job did. Of course, that is largely a reflection on how poor my last sailing job was; but you take what you can.
There is work out there. Just be open to work that may not be just exactly what you may want and work from there. I know that when I went to work for Crowley, I just figured that working on tugs was temporary, since it was below me. I mean, I am a deep sea mariner, after all. I got both an attitude adjustment AND an education that I will never forget or regret. My time on ocean tugs will always be fondly remembered. Yeah, even the tough times of 24 hour + days keeping the machinery together until the next port, only to spend even more time getting the permanent repairs done. But I was a kid and full of energy.