Abstract: A water equilibrating arrangement for a marine vessel comprises a trough that is in fluid flow communication with first and second closed or closeable compartments that are separated by an essentially imperforate structure and a baffle that extends downward from the imperforate structure into the trough and defines a passage that provides fluid flow communication between the compartments. In the event that water enters one of the compartments due to damage to the vessel, water can flow rapidly into the other compartment for equilibrating water load in the two compartments. Flow of gas through the trough is prevented when a substantial portion of the trough is filled with a liquid or a flowable solid or semi-solid material.