Adult cottonmouth jack are usually dark in color, while juveniles are pale with six or seven brown, vertical bars along their sides.

[3] They are named "cottonmouth" because they are distinguished from other members of their family by their bleach-white mouth and tongue.

[4] The cottonmouth jack's dorsal fin has a total of nine spines and twenty seven to thirty two soft rays.

[3] The longest known cottonmouth jack measured 50 cm [5] and the greatest published weight was 2.04 kg.

[2] In the eastern Atlantic, Cottonmouth jack are known from Mauritania to Angola[11] and have also been found off the western coast of South Africa[3] Cottonmouth jack usually swim throughout the water column but they are occasionally seen feeding on the bottom near islands.