I’ve been reminded I should refer to the Estuary formed by the confluence of the Uruguay and Parana Rivers as Rio de la Plata (or Silver River) rather than ‘Plate River’.  I’m still puzzled by why the name exists as all since there’s no ‘river’ of that name, just the estuary and, therefore, why it is not just called the Parana or the Uruguay.  In looking it up I found this photo which shows clearly how much of a different color it is than the ocean and why it is a ‘river’ or estuary rather than a bay.