The locations include nearly any dry sand west of the broken bridge, plus most dry sand east of the bridge.
Possible locations where these items can spawn are shown in red on the map. Cockle (6% Spring/Fall, 5% Summer, 3% Winter).Oyster (19% Spring/Fall, 14% Summer, 12% Winter).Mussel (19% Spring/Fall, 14% Summer, 12% Winter).Clam (56% Spring/Fall, 43% Summer, 24% Winter).Most of the forageable items are avaiable year-round Rainbow Shells and Nautilus Shells are the only season-specific items: Not only does it have several extra sources of forageable items, but also items spawn at a relatively fast rate on the Beach.
The beach is a rich source for forageable items. Locations on Beach where forageable items can spawn.