Wudu by immersion means that one should dip one's face and hands into water, with the intention of performing Wudu. And there can be no problem in performing wiping with the moisture thus acquired, though it is against precaution. Even while performing Wudu by immersion, one should wash one's face and hand downwards from above. Hence, when a person dips his face and hands in water, with the intention of Wudu, he should dip his face in water from the forehead and his hands from elbows. There is no harm in performing Wudu of some parts by immersion, and of others in the usual way.