Marine tardigrades of the family Halechiniscidae (Heterotardigrada: Arthrotardigrada) are reported from Oura Bay, Okinawajima, one of the Ryukyu Islands, Japan, including Dipodarctus sp., Florarctus wunai sp. n., Halechiniscus churakaagii sp. n., Halechiniscus yanakaagii sp. n. and Styraconyx sp. The attributes distinguishing Florarctus wunai sp. n. from its congeners is a combination of two characters, the smooth dorsal cuticle and two small projections of the caudal alae caestus. Halechiniscus churakaagii sp. n. is differentiated from its congeners by the combination of two characters, the robust cephalic cirrophores and the scapular processes with flat oval tips, while Halechiniscus yanakaagii sp. n. can be identified by the laterally protruded arched double processes with acute tips situated dorsally at the level of leg I. A list of marine tardigrades reported from the Ryukyu Islands is provided.