Regarding this, I noticed in the Travel section lesson 2 in the "Select the picture" questions, η βάρκα's image was of a very large vessel that I would label as a ship and the image for το πλοίο was a rather small vessel that I would call a boat.
Link to the section/lesson: https://www.duolingo.com/skill/el/Travel/2
Anyways, those questions don't have a comment section and the only report option doesn't allow comments so I wasn't sure it would be useful. Hope it was alright posting here in lieu of making a thread.
We hadn't noticed that. I'll have a look and if possible it can be corrected in the new version of the tree. thank you for the notification.
The size of the boat/ship is not known from the context therefore both ship and boat should be accepted as correct answers. If you want to teach the difference between πλοίο and βάρκα do it in a sentence that's relevant to it.
Πλοίο is never used to describe a boat, but a ship that's bigger in size. There is no need for context, as these words are not even synonymous in the first place. I don't see the confusion here.
((EDIT)) This comment contained an error. The word removed was "boat". Thank you for the notification. We have removed "ship" and sorry for the confusion. The "hints' are like dictionary definitions so there may be several definitions but not all fit in each sentence. It's usually best to choose the first hint. Here's an example: "Η γυναίκα τρώει στην κουζίνα." under "κουζίνα" you'll see "kitchen" "stove" "cooker" but only "kitchen" fits in this sentence.
Again thanks for your observation.