From Nookipedia, the Animal Crossing wiki
A Clam (ハマグリ. Hamaguri) is a type of deep sea creature found in Animal Crossing: New Leaf. It is a benthic animal found at the bottom of the ocean. It has a circular shadow. Diving is the only way to get it.
Donating to the Museum
In Animal Crossing: New Leaf, an information board in the aquarium will list information about this creature.
"Bivalves shaped like chestnuts, they live in shallow waters and hide in sand when predators approach. They secrete a viscous liquid that gets pulled along by the current and enables long-distance travel. They are popular both roasted in the shell and cooked in a variety of soups and chowders."
Despite being a Fishing Tournament, Chip will still accept deep-sea creatures, but they will not be scored. Chip will say this when given a Clam:
Names in other languages