Former NASA astronaut Garrett Reisman has revealed he once feared he might drown on a spacewalk during his tenure on the International Space Station (ISS) sometime between 2008 and 2010.

Can you drown in space? No one has yet – but that doesn’t mean there haven’t been some close calls.

Reisman revealed on Twitter he had not enjoyed the thought of going down in history as the first person to drown in space when his spacesuit helmet malfunctioned, raising the possibility of his helmet filling with water. 

"Astronaut Tip #217: Make sure your bite valve is firmly attached to your water bag straw," he wrote. "When I saw mine float by INSIDE my helmet I was less than thrilled at the thought of becoming the first astronaut to drown during a spacewalk..."

Spacewalks, or Extravehicular Activity (EVA) – when astronauts venture outside their spacecraft to perform acts of maintenance, installations, or explorations – can last hours. The record is 8 hours and 56 minutes, set by NASA astronauts Jim Voss and Susan Helms in 2001.

In case astronauts get a little thirsty while outside performing these feats, NASA spacesuits have drinking bags inside the helmets that astronauts can bite down on to release water. However, spotting the unattached valve to your water bag floating past you is not ideal, as this means there is a very real potential for a helmet to fill up with water. 

Luckily for Reisman, "the surface tension proved to be enough to keep the majority of the water in the bag," he went on to explain. 

Reisman has not spoken about his near-miss before, and it's unclear when this spacewalk took place, as he conducted three spacewalks during his time on the ISS – but he is not the only space traveler to have been in the running to break that particular record. In July 2013, Italian astronaut Luca Parmitano suffered a similar malfunction but on a much scarier scale. 

During an EVA that was due to last six hours, Parmitano noticed water building up inside his helmet. He informed NASA of the situation at the time, but neither the space agency nor Parmitano had yet realized how serious the incident was.

He remained outside the ISS for 23 minutes, with the water continuing to leak into his helmet, before it began to get in his eyes and close to his nose and mouth and NASA ordered him to get back to safety inside. This wasn't so easy with his vision compromised by the water sticking to the helmet visor, blurring everything. Instead, he had to turn and find his way back to the hatch by feel.

"At that moment, as I turn ‘upside-down’, two things happen: the Sun sets, and my ability to see – already compromised by the water – completely vanishes, making my eyes useless; but worse than that, the water covers my nose – a really awful sensation that I make worse by my vain attempts to move the water by shaking my head," Parmitano wrote of the experience in his European Space Agency blog.

"By now, the upper part of the helmet is full of water and I can’t even be sure that the next time I breathe I will fill my lungs with air and not liquid."

Luckily, he did manage to fumble his way back to the hatch and get inside – though the ordeal wasn't over, as he had to stay inside the suit, water and all, until the repressurizing of the suit was completed. When it was and he could take off the helmet they found between 1 and 1.5 liters (0.26 to 0.40 gallons) of water inside.

“I would say of all the EVA issues we’ve encountered to date, this is probably the most serious one that we’ve encountered,” a NASA spokesperson said in 2014 following an investigation into the incident. “I don’t know of any other failures that have had this potential hazard associated with them.”