Suffolk County police responded to calls that a person was in distress in the Nissequogue River by Kings Park.
Neither dive teams nor choppers have spotted the man believed to be a construction worker who recently moved to the area.
Crews have also deployed a drone and are combing the shoreline on foot.
Locals say that the area where the Nissequogue River meets the Sunken Meadow Creek runs hard and rough water, which certainly played a role.
"It's insane. The current here gets like rapids," Ronnie Farruggia said.
"You look across here you think you could almost walk across but this thing's running at almost 30 miles an hour," Christopher Russell said.
Residents say the swimmer was a construction worker who had just moved here for a job a few days ago.
Neighbor Louis Ramos explained how the man was asking him about swimming.
"He seemed interested in that and he was so happy that he moved here." Ramos said.
Residents are hoping people are reminded of the danger here, which has claimed the lives of even the most seasoned boater for years.
More than a decade ago, NYPD officer Patrick Luca was killed while kayaking with his 5-year-old son, who miraculously survived because he was wearing a life preserver and a whistle.
"Just last season I pulled someone out from under the boat at the end of the dock here," Ramos said.
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