The SEA STAR aquanaut crew during a simulated, underwater "spacewalk." (Image credit: Michaela Musilova)

I was breathing just fine through my life support systems, but I kept feeling an urge to double check that everything was ok with my "spacesuit" before heading out on this "spacewalk." I have worn many different types of spacesuits on Earth during my career, but for the first time in my life, I knew that I couldn’t just stop to breathe the air outside if there were an emergency. That's because I was underwater.

On this excursion, I was leading a simulated space mission underwater called SEA STAR. My " spacesuit " was actually scuba diving gear, and the simulated spacewalks , or EVAs (Extra-Vehicular Activities), included outings where we explored underwater environments. Being underwater, if we encountered a major problem with our gear, we would have had to treat it as seriously as if we were astronauts on the International Space Station .…