According to police, Christian, 28, was nabbed from behind a sand dune at Arichalmunai on the tip of Rameswaram town while a hunt was on for the other person.
The man has been taken into custody for questioning and would be arrested, police said.
A Sri Lankan national who arrived in Rameswaram, India clandestinely by boat from Mannar with one more person has been detained, PTI reported quoting Indian police.