Hi
@Shells, here are pictures of the only two places on the Camino Francés I remember that involved stepping stones across water:
The first one is between Roncesvalles and Zubiri. As you can see, there are solid, blocks of concrete you can safely step on.
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Or you can even walk around it using the road, especially if water levels are higher after heavy rainfall, as you can see on this google maps screen shot:
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The other one is between Melide and Boente. These are big natural stones that are very close together and the water is very shallow.
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For extra balance, use a pair of trekking poles and you should be fine.
Buen camino!