In August, visiting Panama City, I snorkeled the two jetties at
the Eastern side of Panama City and off of Shell Island, in
St. Andrews Bay. You have to take a ferry to the island - a very short
distance.
There wasn't much on the jetties- certainly no calliostoma euglyptum - ,
although I
did leave a large phyllonotus pomum  and did find some nice
cerithium on just one rock. There were many thais hemastoma - Florida
rock shells - everywhere.  In the bay, I was looking for
pecten irradians - in an hour of searching, I actually found ONE pair.
But there were also a few nice dead  olives and other bivalves.

Karen