The long-finned sand diver or tommyfish, Limnichthys polyactis, is a sandburrower of the genus Limnichthys, found all around the North Island of New Zealand to depths of about 5 m, on sandy or gravelly bottoms. Its length is between 3 and 8 cm.

The long-finned sand diver is a small cylindrical fish with a pointed snout, a distinctive undershot lower jaw, and small bulbous eyes that swivel independently. They are pale yellow with black markings. The anal fin is slightly longer than the dorsal fin, and both fins are longer than the very similar New Zealand sand diver. They spend much of their time buried in sand or gravel with just the tip of the snout and eyes showing, and if they are disturbed they dart away to rebury themselves at a new site. They move so fast it is almost impossible follow them, and in consequence are hardly ever seen.

References

• Limnichthys polyactis (TSN 630478). Integrated Taxonomic Information System. Accessed on 19 March 2006.
• "Limnichthys polyactis". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2006 version. N.p.: FishBase, 2006.
• Tony Ayling & Geoffrey Cox, Collins Guide to the Sea Fishes of New Zealand, (William Collins Publishers Ltd, Auckland, New Zealand 1982) ISBN 0-00-216987-8

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