1. The problem statement, all variables and given/known data When asked for the bouancy of a hollow cylinder, containing air, submerged in ocean water. outer radius R. Length of cylinder = L The Material of the cylinder is neglected. I'm thinking the Bouancy (Force) = ρ ⋅ g ⋅ v where v = LπR^2 and therefore F = ρgLπR^2 But the solutions manual states it is F = ρgLπR^2 ⋅ SG, where SG is Specific gravity of ocean water. Why do I need the SG part ?