A crew was out on dirt bikes Saturday morning searching the banks of the Snake River for the man who went missing Thursday night while swimming near Swan Falls Dam, said Andrea Dearden, spokeswoman for the Ada County Sheriff's Office.
The searchers found no sign of the man, whose name has not been released.
Searchers are reevaluating each day to decide how to continue the search, said Dearden on Saturday.
Deputies from the Ada, Canyon and Owyhee county sheriff's offices and members of the Boise Fire Dive Team and Kuna Fire Department began their search Thursday. The man had become separated from his group west of the dam.
Deputies returned Friday and searched the area by air and by boat but found no sign of the man. He was never seen going under the water, officials said.