I had an epidural when I had my c-section. As long as you roll over with your head to your chest the anesthesiologist will have good sight to inject you. I don't recall any pain what so ever. Maybe because I was nervous, but before you know it the injection is done. And to agree with the other lady, you wont feel your legs because of the numbing sensation. But nothing to worry about. You will have no pain.
I should probably clarify...the shooting pain I was talking about was only AS they inserted the epidural and only lasted a second or so. After it's in place, no pain at all.
I had an epidural both times I went into labour. The first time, I was waiting to see if I needed it, but ended up with horrible back labor (and I too thought I had a high pain threshold). Plus, I was induced due to blood thinners, which I've heard brings on stronger, more painful contractions. Anyway, I ended up doing an epidural and it was night and day! No pain after that. I'm not familiar with the water injection, but the epidural can give you almost like an electric shock type feeling when they insert it IF they happen to hit one of the nerves...but that's nothing compared to the labour pains and only if they hit one of the nerves. Of course, a couple of drawbacks is that your legs will be numb (you may not be able to move them at all), and you'll have to get catheterized. Good luck with your decision!