According to this article in the Financial Times, Iran has sent a supertanker, called Happiness I, en route to Asia, carrying 2 million barrels of oil that is off-the-radar literally, in order to obfuscate that it is transporting Iranian oil to another country. When ships are off-radar, they turn off their transponders and are no longer broadcasting their positions.
Off-radar shipping by Iran is in response to the new US sanctions imposed against Iran that come into effect on November 5, 2018.
Although many EU nations appear to oppose the renewal of US sanctions against Iran, their opposition has little effect because oil sales involve the private sector (banks, law firms, insurance firms, refineries, accounting firms), and it is the private sector that needs access to US correspondent banks to survive. Engaging in commerce with Iran, including dealing with Iranian oil, is too much of a risk for the private sector. Even Turkey, which buys 7% of Iranian oil, decreased its purchases by 45%.
Officials are suggesting that the US government intends to ramp up sanctions enforcement against the private sector, mostly as against foreign banks with US correspondents or operations in the US which gives them jurisdiction, that facilitate sanctions avoidance involving Iran or Iranian foreign nationals.