The juveniles have tubular eyes, a feature shared with Taonius, and the broad vanes on the gladius are very distinctive, a useful characteristic for identifying Sandalops.

[4] Sandalops melancholicus occurs in the epipelagic, mesopelagic and bathypelagic zones, like other glass squid it has a pattern of moving deeper as it matures, called ontogenetic descent.

The paralarval eyes are what give this species both its most common vernacular name, sandal-eyed squid and its generic name of Sandalops.

Its head is angled with respect to the body axis and in life the eyes point upwards to the light and have their lower silhouette hidden by the two photophores.

[3] By the time they are sexually mature adults they have reached the bathypelagic zone, below 2000m and it is here that mating takes place.