Prehistoric weapons in water

I recently watched Alice Roberts' new TV documentary "Digging for Britain"on BBC4 and also came across a repeat of Neil Oliver's programme on Celtic Britain on the Yesterday channel. In both, the finding of prehistoric weapons, both bronze and iron, used and pristine, in ancient watercourses was discussed. The prevailing wisdom appears to be that these are ritual depositions. However, I do recall from excursions to North Wales when younger being told by an artist in Capel Curig that it was the custom of the older farmers to store iron tools on the bed of local streams. Their experience was that the tools were protected from rust, presumably because there was practically no oxygen dissolved in those upland streams. I wonder if the practice was a rationalisation of a race memory or if the archaeologists have misread a practical solution to the problem of corrosion on the part of our ancestors.