The activists were set to join the villagers who have buried themselves neck-deep in sand along the shore, demanding the preparations for fuel loading into the nuclear reactor be halted.
On Friday, Satishkumar - a close associate of SP Udayakumar, the activist who is leading the protests - was arrested in Chennai for trying to "instigate" the fishermen there to join the stir against Kudankulam Nuclear Power Project (KNPP).
Meanwhile, the search for SP Udayakumar, the leader of the protesters, is still on, police said. He had announced that he would surrender on Tuesday night, but later did a U-turn.
More than 4,000 police personnel, bolstered by Rapid Action Force, were deployed to maintain strict vigil in Kudankulam town. The Coast Guard aircraft and ships were deployed for surveillance at sea off Idinthakarai during the protests.
The Supreme Court on Thursday had refused to stop the loading of fuel into a nuclear reactor at the Kudankulam plant, while stressing that safety of the people is of prime importance.