A fully inflated, circular survival raft with a diameter of 7.5 ft, floats 9 in. above the SA waterline?

To maintain balance between buoyancy and weight, and thus float, an additional 600 lb of water must be displaced when the lard balls hop into the raft. As W = rho V; and V = Ah we have W = rho Ah and h = W/rho A = 600*12/(62.4*pi()*(7.5/2)^2) = 2.61 inches farther into the water to displace 600 lb. So there is still a 9 - 2.61 = 6.39 in safety margin.