Good cross-training blog here
Good to incorporate some of these non-impact suggestions into your training even if you are injury free, especially if you are ramping up the mileage.
A few personal observations on the aqua-jogging demo video. As the narrator says, there are various ways to do this. I think there are basically two.
1) low-intensity aqua-jogging for recovery - with more of a cyclical running action. At low intensity with a slow-medium cadence you will need a flotation belt. (Peebles pool has some. Just ask.)
2) high intensity aqua-RUNNING to work on your aerobic fitness - with more of a knee-up and heel to bum action, as demo'd by the second guy in the video. If you do this without a belt it is much much harder. Also if you keep your hands streamlined (rather than "paddling" as he suggests) it is harder still. You have to keep a high cadence just to keep your head above the water. THIS IS HARD WORK!
The first guy in the demo video has too much of a forward lean from the hips. Having said that, I don't think you need to get fixated on maintaining "good running form" when aqua jogging or running.
When aqua jogging for recovery, your leg action will be more exaggerated front and back than when running. It's really about getting some mobility and an active but easy stretch into the legs. (If aqua jogging to replace long easy running miles, you will soon get bored and are probably better swimming or cycling instead.)
When aqua running, it is principally about getting your heart rate up. Henry Gray, who many of you will know (coach to Guy Learmonth), is a big fan of aqua running and other pool work, and says in terms of intensity and HR, he can replicate any track session in the pool.
For what it is worth, I myself do sets of 4 to 6 x30s efforts of aqua running (no flotation belt) with a 15s recovery (well TBH these days my recovery goes up by 5s after each successive rep!) and intersperse the sets with some swimming lengths or leg kick. This is definitely enough to get my HR up and have me gasping at the end of the set to the extent that old ladies ask if I'm ok!!!!