Bad hydrometer???

Ok, so I just bought a replacement hydrometer and after brewing a batch of beer I grabbed a sample with my theif and dropped in the hydrometer and it floated so the scale was well above the beer line. So I tried the same thing again only using water this time. Again the hydrometer floated above the water although the numbers were closer to the water line. I've used a hydrometer before and had no problems, but I am new to this hobby so I thought I'd ask if anyone has ever seen a hydrometer do such a thing. It doesn't look like there's anything wrong with it. Seems like maybe it was weighted improperly or something. Ideas??

I'd take it back to the brew shop. Sounds like a bad one.