How does a delta form at the meeting place of sea and river water?

A delta is formed at the meeting point of sea water and river water why?

A delta is formed at the meeting point of sea water and river water. Why?

A delta is formed at the meeting point of sea water and river water. Why ?

Why is delta formed at the confluence of the river with sea ?

A man first swims in sea water and then in river water. (i) compare the weights of sea water and river water displaced by him. (ii) Where does he find it easier to swim and why?