On Tuesday, just off La Jolla, California, the ocean near Scripps Pier looks like the site of a terrible oil spill.

It was not.

The dark coloration of the shallow water near San Diego happened to be a giant school of northern anchovies. Experts say a school of fish this large hasn’t been seen this close to the coast in over 30 years.

Robert Monroe, a communications officer with Scripps Institution of Oceanography at UC San Diego, said he originally thought it was red tide via LATimes.

"It was remarkable. From a distance it looked like an oil slick and you think 'What happened?' and then you get up close and it's amazing," he said. "It's like watching the motion of a lava lamp."

Northern anchovy is known for traveling in huge schools and is commercially harvested in west coast waters according to FIshWatch. Today, the species of fish is used as bait for fisherman to go after larger fish.

What some experts had yet to figure out is if a new branch of the Krusty Krab opened in those shallow waters which would explain the arrival of all those anchovies.