The non-toxic dye was used to stage a fake sewage spill that scientists from the Scripps Institution of Oceanography can study to learn more about the flow of pollution into the ocean.
They want to understand how fast and how far sewage spreads along California's coastline.
The information could change the way officials close beaches, which costs money to local businesses.
The research team took more than two years to set up the financing for the project, that will wrap up in two weeks.
