There’s a difference. The drill ships I believe you are referring to are indeed built mainly in Korea for transocean (example). Some are built in Europe, Singapore. To work in US waters for supers, PSVs must be built in the US and fly US flag. Supermajors only want US flagged vessels providing support to their leased drill ships from Transocean. Federal law requires it as well (Jones Act). The vessel company also must only employ US mariners for work in the GoM which is why our costs are a lot higher than say a company operating in West Africa. They can crew with guys from the Philippines and pay them half of what they pay US mariners.
Most PSVs that work in the GoM are build in southern port areas (some in Louisiana, Alabama, Florida). Four that we have built are all identical and were built at BAE shipyard in Jacksonville.
One thing a lot of people don’t realize is that if all these cruise ships were built in the US, the cost of cruises would be astronomical given that the vessel would be US flagged, have to employ ALL US citizens, and pay tax based on their home ports. Because they are built outside the US and flagged to say…Panama, they can hire whoever they want and not have to pay US tax. Companies typically flag their vessels in the most tax advantageous country. But to have your main port of call in the US requires a shitton more costs. But that’s all the supermajors in the GoM will contract with and that’s all they can contract with if they want to work in the GoM.