[2] Cymatioa cookae reaches up to 11.4 millimetres (0.45 in) in length and has a thin, fragile, oval-shaped shell with a longer posterior end.

The shell has irregular, slightly wavy commarginal striae, or grooves, and fine, dense puncta (minute pits).

Its foot is large and translucent with a bright white stripe down its length, longer than the shell when fully extended.

[2] Cymatioa cookae specimens were first discovered in Baldwin Hills, Los Angeles, when a trench was dug to install a sewer line.

[5] Cymatioa cookae may have been undiscovered until 2018 due to possibly originating from further south, then being transported to Naples Point during marine heatwaves from 2014 to 2016.