The smaller whale may be a calf. This is a rare find because blue whales have been hunted to near-extinction.
The blue whale is the largest animal on the planet.
Blue whales are commonly spotted swimming in pairs according to the Marine Mammal Center.
Local news from across Southern California
About 2,000 blue whales are believed to be living off the coast of California.
This time of year is the annual migration for the California gray and one marine rescue group is urging boaters to steer clear of another whale seen hanging out in the busy harbor at Marina del Rey for the past two weeks.
The whale recently ventured out into the Santa Monica Bay, but returned to the manmade marina's shallow waters.
The Marine Animal Rescue is concerned about the recreational boat traffic in the marina and is working with the Coast Guard to broadcast alerts.