Students at the University of California, San Diego, received an incredible surprise lesson while at the beach this past Monday.  Luckily, the group had a Go-Pro camera in hand to capture this scientific site that hasn’t happened for 30 years, According to KSWB-TV, scientists at UCSD’s Scripps Institution of Oceanography.

A school of anchovies so massive appeared in the ocean, spotted off the coast of San Diego.  These finger-sized fish together created such an ominous presence, that at first site it appeared like a huge dark shadow in the water.

Phil Hastings told the local Fox affiliate that he had no explanation for the massive school of fish, which was 15 meters to 100 meters wide.

“I don’t think we’ll be able to ferret it out,” he said.

The fish were first spotted by a lifeguard, according to KSWB. UCSD students Julia Fiedler, Sean Crosby and Bonnie Ludka then used a GoPro to record the footage, which has been viewed nearly 40,000 times on YouTube.

Watch this video to witness a very rare aquatic phenomenon:

h/t: [ YouTube ]