I've crossed a lot of fast flowing creeks and rivers in the Canadian Rockies, some deeper than my waist. The technique I use, and teach others to use, is to walk facing upstream, and walk sideways, leaning into the flow of water. It ultimately comes down to balance and how sure your footing is, I grew up crossing glacier fed rivers this way, so it was something learned as a child and practiced my whole life.
Depending on the intensity of the flow, you may want to start upstream of where you want to be on the bank on the other side, and back step a little with each side step making your way to your landing at an angle, it's a lot easier to work with the current than it is to fight it. You can use the rocks in the water to help you with your footing, feel for them with your feet as you shuffle them to the side, and plant your foot in front of rocks that feel steady with you heel on the rock. Take small controlled steps so you don't lose your balance, and don't pick your feet up higher than you have to. Step too high or too far and the current is going to take your foot away. I always keep my arms out and in front of me and keep my knees bent for balance, the force of the water is strong, and it doesn't take much to get thrown off, so take your time and don't rush things.
Edit: Here's a video of the technique I describe, while crossing a river in Iceland no less: Crossing a freezing river in Iceland.