Why? (1) Most meteorites are not stable in water. The metal will have rusted and the stone will have broken apart. (2) A meteorite in a stream bed would have had its fusion crust worn off by abrasion against other rocks. There would be no way to identify it as a meteorite unless rusty metal was evident. You are not gong to find a meteorite in a river or stream. Experienced meteorite hunters do not look for meteorites in stream beds or along beaches .