HA! What a coincidence. I was also out snorkeling there this morning. We probably got in the water right at noon. I found it too, just north of the obejcts you mentioned, only I actually picked it up and brought it home. It is made of ceramic and seems to be glazed. A couple little ends broke off. When I first found them, there were three - this time there was only one. If anyone has any idea what this thing is or why it was in the ocean, please let me know.
And while we're at it, does anyone know what the 'Urinal' and the 'water bucket' are? I've seen them before also.