According to Sky sources, the 58-year-old owner of the aqua park and his 30-year-old son are among the dead.
The pair were electrocuted when they jumped into the pool after noticing three children had suffered shocks in the water.
The children were aged 12, 15, and 17, according to the Turkish NTV television channel.
All five victims were rushed to a hospital, however their hearts had already stopped due to the electrocution, according to the hospital.
One other individual has been admitted to hospital in the town of Akyazi with injuries.
Personnel at the aqua park cut the electricity to the building.
Turkish gendarmerie officials said there was no residual current device (RCD) at the aqua park after inspecting the scene.
RCD is a device that instantly breaks an electric circuit to prevent serious harm from an ongoing electric shock.