Grand corruption case involved the alleged purchase of shipping fleets.
There is an urgent need to overhaul rail, ports and logistics infrastructure to cut the cost of doing business and boost confidence.
Organised syndicate member believed to among arrested suspects.
Sawatu is calling the privatisation a Trojan horse for mass retrenchment.
Several reports of protest action led to road closures on Thursday.
High numbers of injuries and fatalities of crew members have made seafarers fearful of launching lifeboats.
According to the ship owner's statement on Monday, the six kidnapped crew members were rescued in Nigeria.
Captain Knowledge Bengu, commander of the SA Agulhas II, faced the challenge of studying while on long sea voyages.
Up to 800 000 seafarers could require training by the mid-2030s to use zero-carbon fuels.
