A "sea chest" used to be the luggage you hauled your gear in when trips were a year or more. (I still have the canvas sea bag I made with needle and palm in the '80s, short trips, 4 - 6 months, so need for a sea chest) It can also refer to a valve manifold of sea suction valves for ballast, fire, SW cooling, GS and bilge pumps.
A "sea bay" is attached to the ship's hull, usually just aft of the fwd ER bulkhead, vented to the funnel by a valved vent. The sea bays, P & S, are connected by a large diameter pipe, furnished with strainers and isolating valves at either end. SW suctions, for the various sea suction chests, cooling, ballast, fire pumps etc, are taken from this large diameter pipe joining the sea bays.
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