The sea cucumber was seized following a tip-off received by marine police.
The marine police informed the forest department personnel, who seized the sea cucumber when it was about to be transported to Sri Lanka in a boat and arrested one person, police said.
Sea cucumbers, classified as endangered species and their harvest banned under the Wildlife Protection Act, are in demand in South-East Asian countries.
Around 500 kg of sea cucumber meant to be smuggled to Sri Lanka was seized on October five from a farm in Mandapam near here.