what is an articial waterway
The answer is a strait.
A canal.
A comparatively narrow passageway connecting two large bodies of water.
isthmus
it is a straight.
An isthmus.
Isthmus
River or Canal
That would be an isthmus.
Straits are a narrow strip of water connecting two large bodies of water.
If it's man-made; it's a canal. If it's natural; it's a strait.
A narrow channel joining two larger bodies of water
Strait Source: http://worldlandforms.com/landforms/list-of-all-landforms/
A strait