A sea-going vessel has mounted on its deck a clam processing plant which includes in sequence a steamer, a clam crusher, a seawater washer, a brine separator, an eviscerator and a chill tank. Special valves are constructed to feed and discharge clams from the steamer which prevents the hot high pressure steam in the steamer from being discharged when the valves are open to the steamer interior. The chill tank includes a special construction to minimize the effects of pitch and roll of the deck while the ship is at sea.