There are many places to hunt shells. Any number of excellent local guides, like Luis Caliz (011-501-226-2785), Tulu at Coral Beach Dive Shop, Tito Alamilla at Ruby's, etc, can take you to places like Robles Point, beaches along the way on the frontside of Ambergris Caye, dredge sites south of San Pedro Town or just north of Cayo Espanto(which are excellent places for shelling), or into Chetumal Bay along the backside of Ambergris Caye.