My feet stung, from the unattended blisters, but I ignored them. The testers flipped the switch, and flames shot up through the corroded metal grates. The leading recruits sounded off the counts; we grabbed the hoses, and heaved. This time I could keep up, my movements were finally smooth and confident like those of the athletic males who led the line. Adrenaline caused us to carry out the shouted instructions with a perfection never yet achieved, every command sunk in deep, and we moved as one.

Though now the night began to wane, the sky turning a shade away from black, no other person moved about the naval training base. This firehouse, however, was alive. We were finally at the brink, the end. This last test was the only thing left of our basic training, the one thing that still held us captive.

I would cut out the commas after "My feet stung, ..." and "The testers flipped the switch, ..." If you are looking to add pause, I think a period or semicolon would be less confusing.

The "though" that starts your 2nd paragraph seems out of place. Shouldn't we expect the base to be emptier at night? I think you're trying to add a sense of place to the opening, but I think you could do it with far less words.

"like those of the athletic males who led the line" makes it sound like a scientist watching a herd of gorillas or something. Wouldn't a person be thinking more along the lines of "This time I could keep up, I felt just as strong and athletic as the men." or something? Maybe even throw in a man's name or two to make it more specific.

I think in general, I would probably not read on. I think the main reason is this sentence: "Adrenaline caused us to carry out the shouted instructions with a perfection never yet achieved, every command sunk in deep, and we moved as one." To me, that sentence saps all the tension from your opening. It tells me that they are doing great, perfect even, and makes me worry less about how it's going to turn out.

You have kind of a danger, action conflict at the open, then that disappears and you switch it to a "Will we finally graduate" hook, and by then you've lost me.