Because of difference in salt concentration.
It does not flow into a sea. It is a tributary of the Rhine River.
Caspian sea and Black sea.
The river Nile flow into Mediterranean sea
A bay is an inlet from either the sea or the ocean.
The Sea of Cortez.
In Caspian Sea
The North Sea
sea breeze
Aral sea.
Irish sea
Arabian sea
Caspian Sea