Writing on his blog from the International Space Station, Parmitano said he felt liquid on his neck shortly after starting the spacewalk on July 16th and was blinded and suffocating as the water slowly rose.
"I feel that the temperature of the liquid is too cold to be sweat and above all I have the distinct sensation it is increasing in volume," Parmitano wrote in a gripping first-person narrative of the incident.
As he slowly made his way back to the airlock, Parmitano said he could feel the water rising in his visor and the audio becoming fainter as the liquid covered the foam fabric of his earphones.
"I don't know if I will have air or liquid in my lungs the next time I breathe…. I realise I no longer know where to go to reach the airlock," he wrote.
Once he was safely back inside the space station and repressuring, Parmitano said he remembered thinking he could open his helmet to let the water out.
"I will probably lose consciousness but it would be better than drowning in my helmet," he said.
The US space agency NASA has launched two investigations into the incident, with engineers focusing on a possible fault in the spacesuit cooling system rather than the inner helmet drink bag.
His spacewalk on July 16th was stopped after about an hour and a half, marking the second shortest in the history of the International Space Station.
The 36-year-old made it safely back inside and was unhurt, though NASA experts said he faced the risk of drowning had the ordeal gone on much longer.
US spacewalks have been suspended pending the investigations.
Parmitano concluded his blog post saying: "The skill of our engineers and the technology we have at our disposal make things that are not easy seem easy.
"It would be better not to forget that," he wrote.