A ship-to-ship transfer is the movement of cargo from one ship to another while at sea, rather than in port. The majority of STS transfers are perfectly legal, utilized to avoid port berthing charges and long port waiting times for large carrier vessels and tankers.
However, some STS transfers are carried out illegally to conceal the origin or destination of the transferred cargo, such as a sanctioned country. Read more about Regulatory scrutiny: what does it mean? and how can STS transfer risk be minimized?