The original piece of embroidery was rectangular. As the finished pebble will be oval, I will extend the embroidery. I want to show you some detail pictures.
At the top left I added a fishing net behind the shell. This loose net forms a nice contrast with the somewhat stiff shell.
I had seen this net on the pebble my friend Susan made.
A few pearls seem appropriate, although it isn't an oyster.
At the top middle a few fly stitches are added and some beads.
More waves on the right.
On the left I added needlewoven bars, extended twigs and ripples, more beads in the dimples in the sand.
At the bottom ripples and beads are added.