Every opening below the waterline on your boat is a potential vulnerability. Seacocks and marine valves are the components that stand between your vessel and an uncontrolled flood. A failed or incorrectly installed seacock valve can allow water to enter faster than any bilge pump can remove it. Since 1948, Fawcett Boat Supplies has helped sailors and powerboaters select the correct hardware for every below-waterline application. This guide explains what a seacock on a boat is, how it differs from a thru-hull, how to choose the right material and size, and how to keep these critical components reliable for the long term.