Seems to me, that they have pretty good intel the Athena is one of AQ's ships, but either they are really not finding anything, or they don't want to say, what they are finding. But looks like they are scrutinizing it carefully.
http://www.intellnet.org/news/2003/10/31/21235-1.html Oct. 31
KUNSAN: South Korea said on Friday it had found nothing unusual on a Greek-owned ship after an investigation sparked by a tip-off it could be carrying members of Osama bin Laden's al Qaeda group.
Meanwhile New Zealand customs today said it would not reveal why the ship that visited New Zealand was subjected to top-level-security checks saying the information is "sensitive".
The vessel, Athena, and its crew were subject to top-level security checks after Customs received "information of interest" about the ship.
The vessel flying the Bahamas flag, arrived in the west-coast port of Kunsan with its cargo of timber on Thursday and was scheduled to stay for up to 10 days.
The Athena visited Auckland and Tauranga before arriving in Lyttelton on October 2 and leaving for South Korea on October 4.