This action by Iran is a simple act of reciprocity after being shafted by South Korea's decision of not releasing ~8 billion dollars worth of Iranian assets.
Surely some of you flamingly jingoistic anti-Iranian bigots (idk what else to call you dolts) can see why Iran would be pissed about such a policy choice on the part of South Korea and would (justly) need to take action in order to send a message as well as up the ante? It's a ship and will be released most likely unharmed but there are consequences to actions, don't give Iran it's own money back?: fine, they'll take your ship as a down-payment. Seems pretty fair to me, it's not like they blew the ship up.
I guess Iranians (to many of you guys) can just die off and blow away when it comes to grave national security matters such as this which have caused great suffering inside Iran due to lack-of-funds. It's like Iranians can't defend themselves or have to adhere to a completely different set of rules just because "mullah bad, or Khomeini-bots", etc., such utterly reckless hatred for Iranians, you would be forgiven if you thought that it was Iran who is the cause of EVERY problem world-wide with the sort of vitriolic unyielding loathing Iranians get.
You don't have to like the mullahs or the Iranian government to see what a horrible anti-humanitarian decision it was for South Korea to withhold ~8 billion dollars of Iran's own assets. That money could have been used (and what have been) to fund COVID relief in the nation for a desperate Iranian populace suffering from one of worst inhumane sanction regimes on the planet. But hey, Iranians barely count as people to you guys right? Just another "Khomeni-bot" country?
I've said this before and will say it again, many slack-jawed mongs kowtowing to a deluded 'American centric' worldview, have sold their own humanity in order to feel superior for some reason. People are people and don't deserve to be treated in such a manner.
E.G.: I don't like Israel or Saudi Arabia (governments or policies) but I wouldn't willingly block their country from receiving funds in order to help their own people fight off a global pandemic that has killed hundred of thousands, since it is cruel and I don't want to stoop down to a low level (couldn't live with myself). It seems many of you have lost your humanity....sad.