Resonator measurements in synthetic media show that sound absorption in seawater is caused by chemical relaxations involving B(OH)3and MgCO3in addition to MgSO4. The MgCO3relaxation can be modeled as a two‐step MgCO03ion‐pair association in which a monomolecular step controls the absorption process. The B(OH)3relaxation involves a similar two‐step association of the B(OH)−4ion in which interactions with thepH buffer system play a crucial role. A number of other relaxations are observed, but their contributions are negligible under seawater conditions.