“What is the basis for claiming that the boats were seized in international waters?”
Bruce, you will have to read the linked article to see. Who are you going to believe? Iran? Your State Department? Or the Navy SEAL? I go with the SEALS!
The guy who wrote that is an ex-SEAL no longer on active duty. It reads to me a lot more like his own speculation rather than anything based on actual inside information or evidence.
Absent uncontroverted evidence, I go with the simplest scenario that makes sense the most logical sense, and that SEAL's speculation doesn't meet that standard.