Day after day, day after day,
We suck, nor breath, nor motion,
As idle as a painted ship,
Upon a painted Ocean.
I think this is a metaphor that is trying to say the sea and the ship are still. In a painting there are still waves, but the author who wrote this stanza -Taylor Coleridge- is trying to say that the water of which they were sailing on was still like a painting but still had a few waves.

October 3, 2016 at 5:02 pm
I’m not sure it’s saying anything about waves really. The main point is that a painted ship is eternally still. I think the power of this simile is that it suggests permanent and absolute stillness.