Singapore's Immigration and Checkpoints Authority (ICA) said officers at the Woodlands Checkpoint were informed by the Police Coast Guard of a suspect walking along the shoreline at about 3am on Sunday.
Officers were immediately deployed to search for the person and about half an hour later, the suspect was arrested.
Based on preliminary investigations, the man had tried to swim to Singapore from Johor, Malaysia and reached the shoreline where he was arrested. The man was not named.
The ICA said that it takes a serious view of attempts to overstay, enter or depart Singapore illegally.
Investigations are ongoing, the ICA said.
In May, eight Bangladeshi men working in Singapore who were planning to stage terror attacks back home were detained under the Internal Security Act (ISA).
