It has been 48 hours since Bradly Alexander Sr., 41, of Fayetteville, was rafting the New River with his 21-year-old son.
The son managed to make it safely to shore, but his father was last seen swimming without a life jacket.
Crews brought in cadaver dogs Friday.
"They're gonna take a dog out there," said U.S. Park Ranger Eric Oaks. "He's trained to smell out the subject on the water, and he's trained to be able to locate the scent from him."
U.S. Park Rangers said high water levels are making the search difficult.
Alexander was guiding the raft about 2.5 miles upstream from Stone Cliff Bridge when he disappeared, and rangers say the area has rugged banks, steep terrain, and railroad tracks so there is limited access to the river.