The density S of coater of bulk modulus B at a depth y in the ocean is related to the density at surface so by the relation.
Bulk modulas $ B = -V_o { \triangle p \over \triangle v } \Rightarrow \triangle v = v_o { \triangle p \over B } \Rightarrow v = v_o [ 1 - { \triangle p \over B } ]$ $ density \rho = \rho_o [ 1 - { \triangle p \over B } ]^{-1} = \rho_o [1 + { \triangle p \over B } ] $