A novel Gram-stain-negative, rod-shaped, non-flagellated, strictly aerobic strain with gliding motility, designated SW024(T), was isolated from surface seawater of the South Pacific Gyre (26° 29' S 137° 56' W) during the Integrated Ocean Drilling Program Expedition 329. Phylogenetic analyses based on 16S rRNA gene sequences showed that the novel strain was related most closely to Aquimarina muelleri KMM 6020(T), Aquimarina macrocephali JAMB N27(T), Aquimarina addita JC2680(T), Aquimarina mytili PSC33(T), Aquimarina intermedia KMM 6258(T), Aquimarina latercula ATCC 23177(T), Aquimarina spongiae A6(T), Aquimarina agarilytica ZC1(T) and Aquimarina brevivitae SMK-19(T) (96.1, 95.5, 95.0, 94.4, 94.3, 94.0, 93.4, 93.3 and 93.2 % similarities, respectively), demonstrating that the novel strain belonged to the genus Aquimarina. The DNA G+C content of strain SW024(T) was 30.8 mol%. The major respiratory quinone of strain SW024(T) was MK-6. The dominant fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 1 G, C16 : 0 10-methyl and/or iso-C17 : 1ω9c, and iso-C15 : 0 3-OH. The polar lipids of strain SW024(T) were phosphatidylethanolamine, three unknown aminolipids and five unknown polar lipids. On the basis of combined phenotypic and phylogenetic analyses, strain SW024(T) represents a novel species of the genus Aquimarina, for which the name Aquimarina longa sp. nov. is proposed. The type strain is SW024(T) ( = CGMCC 1.11007(T) = JCM 17859(T)). An emended description of A. muelleri is also proposed.