Evgenia Sviridenko, 24, had apparently been using her phone to check her social media page on VKontakte - the Russian version of Facebook - as she bathed.
"Her body was still shaking from the shock"
However she apparently lost her grip on her phone, which was charging at the time, and dropped it into the water with her.
Her flatmate Yaroslav Dubinina said: "I noticed that she had been gone a while, and when I couldn't raise her I opened the door and saw her floating on the water looking pale.
"I saw her phone which was on charge at the bottom of the bath.
"Her body was still shaking from the shock."
It remains unclear as to why the charger did not cut out when it came into contact with the water, or whether Evgenia was using an official Apple charging product.
The company have previously released statements on their website warning of the dangers of using unofficial iPhone chargers, saying: "Recent reports have suggested that some counterfeit and third party adapters may not be designed properly and could result in safety issues."
Moscow police are currently investigating Evgenia's death.