What type of fish was this?

I saw this fish in the ocean where I was swimming in South Carolina. It looked like a piece of seaweed or long blade of grass. It was about 6 or 8 inches long, yellow green in color and didn't appear to have noticible fins but swam by wiggling side to side. It had a pointed face and two somewhat large eyes. I would really like to know what type of fish this is, I'm very curious. I know it wasn't just a piece of seaweed or grass because it was clearly alive and moving itself. Thanks.