For me, the $10 Glock mag pouch works better than all the other pouches in the shoebox, and it can be tweaked to fit some M&P mags.
Excellent video, gonna invest in a couple of those pouches. Can anyone say stocking stuffers? (I know I know, it's kinda early)
http://www.safariland.com/magazine/magazine-holder-clip-on-11229.html One our local LEO's turned me on to these over a decade ago. I have several. They are cheep, light, and effective.
This is the first I've seen that mag holder. It looks excellent. Can the mags get knocked off the clip accidentally? (Cool diving site, by the way. Awesome pictures.)
Yes it can get knocked free, but it very seldom happens for me. I mainly use them with standard full-size mags, so about 1/3 of the body sticks up over the top of the clip. So there is some leverage that can push them out and body shape and carry style can effect this. In well over a decade of using this it might happen to me once a year where the mag pushes out, but I have never had it fall all the way out. With my other I generally keep a .380 mag in it so basically a very small part of the mag sticks over the clip and I have never had the push out problem with them. Thanks for the comment on the dive site. I just added a couple more links that people might enjoy.
I've had the Fobus Roto Paddle Double Mag Pouch for a while now, it has worked really well for my M&P9c magazines (also holds the full size). Never had a mag slide out. The Glock model looks interesting though, I may have to consider getting one and giving it a try.