Scientists were back out along Imperial Beach Thursday, a day after releasing bright pink dye into the water.
"What we're doing is we're putting fake 'pollution' in the water and we're tracking it," Professor Falk Feddersen with Scripps Institution of Oceanography said.
Teams were stationed in green tents, guarding instruments that measure the concentration of dye in the water. The bright pink dye is non-toxic.
They also track it with jetskis and underwater vehicles.
Feddersen hopes by following it up and down the coast, they'll figure out how pollution moves so they can protect the environment.
He said they plan to release pink dye into the water two more times over the next month.
Researchers from the Scripps Institution of Oceanography, Jacob School of Engineering and several Mexican institutions are taking part in the project.
The project started September 22 and will last until October 17.