Yes, it is called the mouth of the river.
Name Of Place Where River Empties Into Larger Body Of Water? Is It Mouth?
The estuary is where the river meets the ocean. It has a mixture of fresh water from the river and salt water from the ocean. The mouth of the river is the same as an estuary, but estuary is probably the word they want.
The mouth of a river is where it flows into an ocean, sea, desert, estuary, lake or another river.