Not shell-related either, except that I was shelling at the time, but
attesting to the strength of gulls.

In the dunes at some gorgeous beach on Cape Anne, Massachusetts:  I think I
established my "base" and put my belongings too close to some area that
some gull apparently regarded as its "home territory".  The first time I
went down to the beach for a short swim, the gull deposited my rather large
towel about 50 yards from where I had put it originally.  Well, I liked
that spot, so I put the towel back.  The next target for the gull's attack
was, behind my back, a (not very heavy) pocketbook that I had tossed aside
when I didn't feel like reading anymore.  The book, however, slid out of
its beak and landed only about a yard from where it had been originally --
a not very successful attempt.  That must have made our protagonist quite
mad, because before I knew what hit me the gull dived down directly in
front of me and snatched up my lunch -- a large brown paper bag with a
one-liter bottle of water, nearly full, and a sizeable sandwich!  It was
able to fly with this heavy bounty for over 100 yards before the paper bag
had torn to the extent that my lunch came tumbeling down and ended up in
the sand, the sandwich squashed, the bottle intact.

Well, I went to some other part of the dunes after that...  Don't mess with
gulls!

Monika
(back, and living in sunny San Diego now!)