Thanks Paul:
 
Littorina were the specific mollusc I was wondering about.
 
I have collected on the Northern Coast of Iceland during one of my
government sponsored vacations, and saw a fair variety of bivalves and
things that eat them and all were below the water line.
 
About the only places I have looked but seen any molluscan life was in
the suburbs of Thule Airbase in Greenland where there was a rounded-rock
shoreline for a brief summer period with only algae seen on the beach.
The same for Baffin island where there was only an ice beach either
summer or winter while I was there.  Never did venture into the water in
these arctic places.
 
I had never given the freezing problem for molluscs a thought previously
but did experience it with my ears a few times.
 
Aloha,
 
Wes