Here's a happy ending to a pretty upsetting story: Above, you can see a gang of sea lions bounding happily (and floppily) toward the ocean, seemingly thrilled to be returning home. But they overcame a lot of adversity to get to their happy reunion with the sea.

As you've read here before, California is dealing with record numbers of sick and stranded sea lions. Here's some background from a previous post:

When water gets warmer -- as it has this year, because of the El Niño weather pattern this winter -- food for sea lions gets scarce. That probably means that mama sea lions spend more time away from their pups looking for food to keep themselves alive. When left alone and starving for long periods, sea lion pups are more likely to wean themselves early.
And when they leave home, they're doing so not just too young to fend for themselves, but already hungry and desperate.

These particular sea lions were being rehabilitated at the Pacific Marine Mammal Center in Laguna Beach. On April 28 -- the day before they were set to be released -- the sea lions were victims of what appears to be a malicious attack. When a worker went in to check on the sea lions, she found that they'd fled their saltwater pool. When she felt chlorine fumes stinging her own eyes, she knew why. Their enclosure had been contaminated with enough chlorine to cause chemical burns. Of the 17 sea lions in the enclosure, 15 had open sores on their corneas.

On Tuesday, 14 of the sea lions from the attacked group were successfully released. But the attacker is still unknown. The Los Angeles Times reports that all the chlorine that should have been on-site was accounted for during police investigations, which makes detectives think the incident must have involved someone bringing in chlorine from the outside -- not some worker from the facility accidentally dumping some in. Police and rescue workers alike are baffled as to what might have inspired such a needlessly cruel act.

If you have information about who might have attacked the sea lions, you can call Laguna Beach detectives at (949) 497-0377 or the National Oceanic and Atmospheric Administration (NOAA) hotline at (800) 853-1964.

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