Why the Pacific Ocean turned pink off an area of the Southern California coast

Pink-tinted waves rolled onto a San Diego beach in Southern California on Jan. 20, offering anyone walking along the beach an unlikely sight.

The Pepto Bismol-colored waters were seen at Torrey Pines State Beach and Natural Reserve, where Scripps Institution of Oceanography at UC San Diego is conducting an experiment.

University researchers injected nontoxic pink dye into the water to observe how freshwater from inland areas such as rivers and estuaries interacts with the surf zone when it flows into the ocean.

Scripps said in a statement posted online that it's partnering with the University of Washington for the experiment, which will continue into February. The first dye release, on Jan. 20, is slated to be followed by two more, in late January and early February.

When rivers and estuaries pour into the ocean, they carry sediments and contaminants, and "little is known about how these plumes of more buoyant, fresher water interact with the denser, saltier and often colder nearshore ocean environment, particularly as the plumes encounter breaking waves," the institution said.

Researchers are pouring the pink dye into the freshwater within the reserve's estuary, and it allows them to track and study the water as it flows into the ocean.

"I'm excited because this research hasn't been done before and it's a really unique experiment," Scripps coastal oceanographer Sarah Giddings, who is leading the study, said in a statement. " ... We will combine results from this experiment with an older field study and computer models that will allow us to make progress on understanding how these plumes spread."