Manuel,
 
I have been traveling in Sri Lanka and the Maldives last year. Relating to Sri
Lanka, I experienced that beach collecting of shells is done a lot by locals in
the early morning to sell the interesting shells to tourists. By diving and
snorkeling you can collect around the reefs. Note that some areas, especially
around Galle have heavy waves to snorkeling/diving is virtually impossible. In
the tourist areas a lot of fresh (sometimes very fresh, including scorpions in
the shells, be aware) collected shells are offered. You  have to ask the person
selling the shells that you are interested in special shells, so they bring you
to their contacts. On the beach they only offer big shells (Murex Ramosus, and
that kind of stuff). With the "dealers" you will find for instance Lyria
cloveriana offered in substantial numbers for a few dollars and a lot of
interesting stuff.
 
In the Maldives I only visited the island Kuramathi in the Rasdu-Atol. I
experienced that live collecting by Scuba is not allowed. Also, live collecting
by snorkeling is not allowed, however this is not actively enforced. When
leaving the Maldives, my lugage was scanned but there was no reaction on the
collected shells. Maybe they were sleeping, but it seems to be allowed to export
shells. BTW, diving / snorkeling is great in the Maldives. The islands are so
small that you will always have a beachfront room and you can take a morning
dive in the huge salt water tank in front of your room.
 
 
Greeting,
 
Fred L.J. Vervaet
The Netherlands, Amsterdam