The quote you have indicated in your question is a full stanza that comes from the second section of this great poem and comes directly after the mariner fatefully killed the albatross that is recognised as being such an important symbol of nature. One of the consequences of killing this bird is that the ship that the mariner and his crew are sailing on suffers a complete absence of wind to propel it on its journey. Consider the full quote to see how this is described:
Day after day, day after day,
We stuck, nor breath nor motion;
As idle as a painted ship
Upon a painted ocean.
The repetition of "day after day" emphasises the length of the time that the ship faced without wind, and the simile in the last two lines, where the ship is compared to a painting of ship also reinforces the idea that the ship is static and can't actually move at all in its "idleness." The results of the mariner's unthinking action are coming back to haunt him.