Specifically, what kind of woodwork would be done on a derrick barge? I’m applying for a carpenter position, but don’t have experience on one of these boats.
My guess would be industrial carpentry. Cutting large timbers for under dock framing, building wood scaffolding in awkward places ect.
Historically in the Puget Sound region carpenters and pile drivers have had the same union representation, the job title could be an artifact of similar labor relations in your area. As rshew stated there is plenty of work with pilings and timbers around the waterfront. There might be some forming for concrete pours too. At least around here timber piles are becoming undesirable due to environmental regulations and one might find themselves dealing with lots of steel sheet pile and steel or concrete pilings too. You could easily find yourself spending a lot of time around a cutting torch.
I’d suspect that one would also spend a considerable amount of time rigging hoists for the crane to pick. Proper rigging is serious business and if they would don’t offer provide training per the roles defined in ANSI/ASME B.30.8 I’d be concerned about their overall safety program. If you get an interview ask who does the rigging, who runs the crane, who is the lift superviser, and what formal qualifications they have (the era of OJT for these folks is coming to an end). Depending on how sharp the regulators are in your area barge mounted cranes/derricks may not receive much in the way of inspection or regulation and we all that sometimes that doesn’t make a safe work environment. If the work is being performed for national/international name contractors or the federal government there will be plenty of other external oversight to keep things in check.