As in the case of all rivers which flow into seas or oceans, the Nile River mixes its fresh water with the salt water of the Mediterranean at its delta. There is no exact point at which a river ceases to be fresh water and become salt water.
Yes. Because even though rivers run to merge with salt water rivers flow down so there is no salt water in a river making it 100% fresh water. Yes. Because even though a river runs to merge with salt water, rivers flow down. Therefore, making a river 100% fresh water.
The Charles River is Fresh water but has traces of salt from the locks the separate the river from Boston Harbor. When the locks open and close very little salt water gets into the river, but all in all, it is fresh water.
Sorry for this short answer... Earth. A briny water ecosystem can contain both salt and fresh water, though it is all mixed together. These ecosystems are where a fresh water source, such as a river, meets a salt water source, such as an ocean. River deltas commonly have briny water.
The Sea of Galilee has fresh water, fed by the River Jordan. The salt content is beginning to increase from salt water springs in the bed of the lake because too much fresh water is being extracted, but it remains a fresh water lake at present