The second man, a 37-year-old Morris Township resident, remains hospitalized. Authorities did not release his identity or condition.
Witnesses say the men became submerged in Indian Lake in Denville at about 2:45 p.m. Sunday.
Rescuers quickly pulled one man out with the help of a nearby resident, but the other man was harder to reach and remained in the chilly waters for about 30 minutes.
Investigators were trying to determine why the men were on the lake and what caused them to fall in the water.
--- Information from: The Star-Ledger, http://www.nj.com/starledger