I’ll be a thorn in the side here. First here is a theoretical example of a tug which is going to be towing a barge of cargo from Houston Tx to Cartajena Columbia. Using the logic that a ‘near coastal’ license could cover the trip like you are trying to justify, and as per Mr Cavo’s implication, Your company HR office would have to ensure that your license is ‘accepted’ by Mexico, Belize, Honduras, Nicaragua, Costa Rica, Panama, and Finally Columbia. So your office would have to ensure all the countries accept your license. OR… They could just hire a mariner with an Oceans endorsement and not have to worry about it. What do YOU think any office would do? Secondly, if there was a voyage being undertaken from say Houston Tx to say The Yucatan Mexico, but half way there, they got a change in orders to take the load to aruba, do you really think the office would accept having you jaunt in looping courses just to stay within 200 miles to keep the near coastal license valid? NO. Hiring an ocean license would let them send the boat the most economical course, to save money. The difference in personel cost between a near coastal versus an ocean endorsement is marginal. Huge waste of fuel is an unacceptable expenditure.
Your query about whether having one oceans license would ‘cover’ the trips is incorrect. The vessel either needs the wheelhouse complement to be oceans, or not. you cant piggyback off one another. If the particular trip requires an ocean license, then ALL operators must have an ocean license.
From my limited knowledge of this, only Mexico, the Bahamas, and Canada accept our licenses as ‘near coastal’ being acceptable to operate from their near coast. BUT, this is a very difficult thing to find out, and I don’t know of any company which will put the time in to figure this out. They just swap crews to make the trip with ocean licenses.
Of course your friend could just ‘go’ and try it. In all likelyhood it wouldn’t be discovered, unless there is an accident or investigation upon return. The he may simply have his license revoked. So yes, you could just ‘wing it’ and see if he gets away with it (provided you found a company to hire him on such voyage as an officer).