The tax penalty goes away in 2019. It is still in place. So until then US tax payers may still get the 2.5% tax penalty - pro-rated for the months you do not have ACA (Affiodable Care Act/ Obamacare) compliant insurance.
None of the international individual plans are ACA compliant unfortunately. I do have an inexpensive Catastrophic plan that is exempt from the tax penalty that one can buy to supplement your international policy.
There is a group plan that IS ACA compliant. One needs a US corporation to have this plan and a minimum of 2 members, not married, unless they both work on the vessel.