Attached pictures of two findings from the beach of north-west Crete.
I would love to know what they are (at first glance I thought it was a fossilized tooth, but I'm not so sure).
You have a modern worm, probably a serpulid worm, encrusting a pebble. it looks lik it may have dissolved some of the pebble in the processing of making its tube (or maybe it is just a trick fo the light in the photo).
The other one looks a bit like a mammoth tooth, but we could really do with somebody else's opinion on that.