325. A vessel has a cargo hold divided by a shaft alley into two tanks, each 35 feet long and 20 feet wide. Each tank is half filled with sea water. The vessel displaces 5,000 tons. What is the reduction in GM due to free surface effect?

The free surface correction is calculated by summing the second moments of area for each tank, multiplying by the liquid density (1/35 ton/ft3), and dividing by the vessel's displacement (5,000 tons), resulting in a reduction in GM of 0.27 feet.