Just for information, the Loire river (one of the largest and longest french river) is almost never over 3m deep (except during floods). In most of it's course, you can cross it on foot (but of course, you are not dry at the end). In Tours, where I lived, average depth is a bit over 1m (and width just below 800m). Just above Orleans, where my mother's family lives, average depth is around 2m.