Is it permissible, in Islamic law, for the family of a young man who drowned due to the negligence of officials to take the compensation money resulting from the negligence case? And is it permissible for them to use this money for a جاریة (ongoing) charity? And would that harm the deceased?

If the rescuers are found liable, the young man's family can sue them, and the compensation will belong to all the heirs of the drowned person. If the adult, sane heirs agree to donate the money as an ongoing charity on behalf of the drowned person, it is a good deed and will not harm the deceased. However, if no transgression or negligence is proven against the rescuers, the young man's family has no right to any compensation.