Aydin, I've always been tempted to write "1 bomb" on the customs
declaration, just to see if anyone actually reads the things.  Never
had the nerve though.  I don't look good in stripes.
Sam, you should normally have no problems sending non-protected
shells out of the country.  By "normally" I mean in the absence of
some unusual situation like a war or a postal strike in the country
of destination.  I send parcels out of the country frequently.
Naturally, they should be well packed, in a strong carton which is in
good condition.  If the bottom flaps of the carton are not glued, glue
them.  It doesn't hurt to also run a bead of glue up the corner seam.
Tape the box well with package sealing tape.  Print the address
clearly, directly on the box, with an indelible marker.  Don't use
any kind of stick-on labels - they can fall off or be torn off.
Don't use an outer paper wrapper over the box - again it can be torn
off.  And don't tie the box up with cord or rope - this is no longer
allowed.  If the parcel is not very large or heavy, I recommend using
the "air mail small packet" rate.  It is fast, safe, and not too
expensive.  Also, small packets are rarely opened by customs.  Unlike
Aydin, I have never sent a parcel outside the country without being
required to fill out the appropriate customs declarations.  For items
sent under the small packet rate, all that is required is a little
green sticker that takes about 15 seconds to fill out.  In the
contents section, write "sea shells for scientific study".  In the
value section write 0 (zero) (otherwise the recipient may have to pay
import fees on the declared value).  In the little boxes at the
bottom, check off "gift".  That's all there is to it.  Of course, if
the shells you are sending are monetarily valuable, and you want to
insure the parcel, then you have to declare the actual value, and the
recipient will have to pay the fees.  Sorry, I don't have the specific
size and weight limits handy for small packet service, but it can be
used for a fairly average size box, not just tiny things.  For larger
boxes you will have to choose between air parcel post and surface
mail.  Air PP is rather expensive.  Surface mail is S L O W, and has
a greater risk of loss or damage.  For both of these, a longer
customs declaration is needed, but still no big deal - takes maybe 2
minutes to fill out.  You have to fill in the name and address of the
sender and the addressee, plus the same information needed for the
small packet sticker (which should be filled in as noted above).
Small packet to Europe takes 1 to 2 weeks, average 10 days.  To the
western Pacific area, average 2 weeks.  Surface mail can take 2
months or longer, depending on how many other ports the ship is going
to, and how long it remains in each port before moving on.  In the
past year I have sent about 40 parcels to 16 different countries, and
all have arrived safely.
Regards,
Paul Monfils
Rhode Island