The ruins of the church-whose age is as yet unclear-were discovered during dives by an underwater archaeologist, said Uğur Topalak.
The depth of the lake ranges between 10 and 15 meters (33-50 feet) and it has a surface area of almost six hectares.
Over the millennia, Turkey has been home to people of various faiths, from ancient pagans, Christians, and now largely Muslims.
Turkey has worked to respect and restore remains left by non-Muslims. Topalak said that Lake Gaga, which is a natural protected area, will also be registered as an archeological site.
