Saw a light in the sky moving erratically, zig zagging and changing its rate of speed.

We were on vacation and crossing the ferry from Vermont to Plattsburgh. Saw the light on the ferry while looking at the stars. We could still see it when we got to our hotel. The light mostly was going in one direction, about the same direction the ferry was going in (from Grand Isle VT to Plattsburgh, NY). The light was bright enough to stand out from most stars.
 What made it strange was it’s erratic behavior. It was stopping and starting, sometimes it would reverse in the opposite direction, but rarely. It would zig zag and change speeds. It reminded me of how electricity / water follows the path of least resistance, or how a drop of water falls down a wall in a shower, sometimes it would slow down and then speed up, etc.
 The phone camera couldn’t capture it as the object was too far away.
 I would just like to know if anyone else saw it, because it should be obvious to anyone looking up at the stars that night in the area.