Is this a cowrie?

Sorry for the size of the critter in the photo. It is really really small about 2cm in length and I was using a 18-70mm Nikon lens for the first time and I didnt know how close I could get to the critter for a good focal length. I took two photos, had to surface for air and when I swung back around it was nowhere to be found.

I can see why you would think that but it's actually a bubble shell, Micromelo undata. These are shelled opisthobranchs that eat worms.

Wow, your good! I looked up the Micromela undata and found this info as well http://www.seaslugforum.net/factsheet.cfm?base=micguam . I am in the East China Sea which I neglected to mention. To my untrained eye they both look the same.