They have variable markings, including a black patch on the shoulder girdle, reddish-brown vertical bars across the back, and thin yellow-gold striped lateral lines running from behind the gill flap or operculum to the base of the tail or caudal fin.

The etymology of Synodus is of Greek origin: syn, symphysis or grown together, and odous, which means teeth.

The study also identified the suborder Alepisauroidei as the largest and oldest known vertebrae clade with the reproductive strategy of simultaneous hermaphroditism.

About eight pairs of reddish-brown bars are on the top and sides of the body, broadest at the lateral line and narrowing towards the belly.

[10] The anal fin of the sand diver has 10-12 soft rays which distinguish it from the otherwise similar diamond lizardfish (S. synodus) which has eight to 10.

Another fish with which it might be confused is the Atlantic lizardfish (S. saurus), but that species is uncommon in the Caribbean and has slender, blue or turquoise longitudinal lines.

The tongue has five rows of teeth, the largest positioned closest to the anterior tip, slanting toward the back.

[7] Sand divers are found in the subtropical western Atlantic Ocean between 37 and 17°N, the Caribbean Sea, and the Gulf of Mexico.

Their range extends from North Carolina and Bermuda, southwards to Santa Catarina in Brazil, and includes the West Indies, Caribbean Sea and northern, eastern, and southern Gulf of Mexico.