Do you have any flashing lights with this? How is your vision in that eye?
This sounds like you are having a vitreous detachment. There is a gel-like substance called the vitreous in the inside of our eyes. As you age, the gel breaks up into little pieces and floats around. Eventually, over several months, the floaters settle down and you don't see them all the time.
Rarely when this happens, the retina may become involved and torn. When someone has these symptoms, I suggest that they have their eyes checked to make sure the retina is OK. This is not an emergency for you at this time. However, if you notice flashing of lights or shadows closing across your vision, you should have your eye checked right away.