Psammogobius biocellatus is a goby which varies in colour from dark brown to blackish, marked with rows of small black spots along its flanks and 2-3 dark blotches along the back and upper flanks. There is a dark band on the first dorsal fin with more dark bands on the lower part of the caudal fin and narrow bands on the pelvic fins. It attains a maximum total length of.
The sleepy goby occurs in the intertidal zone in estuaries, lagoons and coastal rivers, often amongst mangroves where it burrowing into the silty-sand substrate, it may also be found in the lower reaches of freshwater streams. It buries itself in the sand.