Hey ettim,
I'm working on my cert and did the swim test this summer. I'm certainly not in good shape - not an ironman swimmer - that's for sure - but didn't have a problem with the swim test. A few pointers:
1.) When you start, you might be able to push off - if you can, I can normally cover about 1/3 to 1/2 the pool before stopping - so, there's 1/2 lap!
2.) When I was a kid, I was on the swim team - so I've just always been able to swim as long as I can remember - make sure you keep your fingers together. When you bring your arms around, try not to splash - you can sort of extend them and slip them into the water - this reduces drag, conserves energy, and makes your swimming more efficient. On the downstroke, it's not straight down - instead it's more of a ... woman's shape actually

Or 1/2 of a figure 8 - or a bowling pin. pick your favorite shape - but the point is, that if your hand does a curve or two, this extends the time you're thrusting it through the water and providing propulsion for your body. Remember to keep a steady kick, every little bit helps. Breathing - when you're racing, you don't breath in until you have to - so you might see a sprinter take 5-10 strokes before breathing in. Of course, they're breathing out for a lot of that, slowly, through the nose. When you're ready to breathe in, a quick turn of the head into the slipstream of your
arm that is back and the water should actually be forming a pocket there, and you're done.
3.) The swim isn't timed - so don't race. I did a bunch of strokes - I would do the crawl (freestyle) until I got tired, then switch to breaststroke, then to side, then to back. If you lose your breath, turn over on your back and
kick only. You can move along with a kick - and just rest your arms and upper body and get breathing back under control. Just keep it slow and steady and you should have no problems.
Hope this helps.