A Gram-negative, aerobic, rod-shaped (0.6-0.9 × 0.7-1.2 µm), motile marine bacterium, designated MEBiC06554(T), was isolated from seawater collected from the East Sea, Korea (also known as the Sea of Japan). 16S rRNA gene sequence analysis revealed that strain MEBiC06554(T) was affiliated to the order Kordiimonadales and showed high similarity to Kordiimonas gwangyangensis GW14-5(T) (95.4 %), but formed a distinct phyletic line. Growth was observed at 10.5-35.0 °C (optimum 20 °C), at pH 5.0-8.0 (optimum pH 7.0) and with 0-13 % (w/v) NaCl (optimum 3.0-3.5 %). The predominant cellular fatty acids were iso-C(15 : 0) (14.9 %), iso-C(17 : 1)ω9c (44.6 %), iso-C(17 : 0) (6.3 %) and summed feature 3 (comprising iso-C(15 : 0) 2-OH and/or C(16 : 1)ω7c; 13.9 %). The DNA G+C content was 50.3 mol%. The major respiratory quinone was Q-10. Phosphatidylethanolamine, two unidentified glycolipids, six unidentified aminolipids, three unidentified lipids and one unidentified aminophospholipid were detected as major polar lipids. On the basis of the data from our polyphasic taxonomic study, strain MEBiC06554(T) should be classified within a novel species of the genus Kordiimonas, as Kordiimonas aquimaris sp. nov. The type strain is MEBiC06554(T) (= KCCM 42940(T) = JCM 16665(T)). Emended descriptions of the genus Kordiimonas and of its species Kordiimonas gwangyangensis and Kordiimonas lacus are also proposed.