Thirty-one-year-old Ercumen dived 110 meters in two minutes, 40 seconds.
Following her dive, she unfurled a Turkish flag and banner reading: “One breath, one heart for our martyrs."
"We would like to make a name for our country, not with terror or coups, but with such international successes," she told reporters.
"One breath, one heart," she also wrote on her official Twitter account.
Ercumen already holds four world records in free diving as of 2013.
At least 241 people were martyred and nearly 2,200 injured in the failed coup which the Turkish government said was organized by followers of Fetullah Gulen, the Fetullah Terrorist Organization (FETO) leader who lives in self-imposed exile in Pennsylvania, in the U.S.