She did an undergraduate degree at the College of Creative Studies at the University of California Santa Barbara in the United States.

[5] After completing her thesis in 2008, Marshall stayed on in Mozambique to spearhead the conservation efforts of this species along this remote African coastline.

In 2009, Marshall co-founded the Marine Megafauna Foundation with fellow classmate Simon J Pierce to establish a manta ray and whale shark research program.

While part of the International Union for the Conservation of Nature Shark Specialist Group (SSG) Marshall wrote the first UICN Red List assessment for manta rays.

She also appeared on the show Wild Things with Dominic Monaghan on BBC America and 'Man to Manta' with actor Martin Clunes.