Prefer the non-stretch to stretch
I used the built-in elastic wader belt but I doubt it would shut down the water influx if I went for a swim. The belt isn't tight enough (even if cinched down, there's still that elastic give), and it's too high on my waist (just below the sternum).
I use two additional non-stretch nylon belts (one to hold a sheath containing long nosed pliers and a flat double cut file) at naval height to keep the water out. The bad news is that in the past, my back has got soaked even as my crotch and legs stayed dry.
I continue to be surprised at how many anglers I see without wading belts, or with loose ones.
The method doesn't matter to the fish.