I took my kids to SeaWorld. Not just once, but multiple times.

I remember experiencing what I call the “cringe factor”—when you know you’re watching something creepy but it’s not quite appalling enough to make you get up and leave. I’d sit there, uncomfortable, anesthetized by thumping music, bright colors and smiling faces. I’d watch a trainer stand on the face of a killer whale, surf its back, spin it in goofy circles, and I would instinctively feel I was beholding something demeaning. But then I’d look around the stadium and see hundreds of people smiling and wonder “how can something that makes so many people happy be such a bad thing?”

On February 24, 2010, Dawn Brancheau, a top SeaWorld trainer was killed by Tilikum, a 12,000 pound killer whale. I began researching the story for my next documentary because I couldn’t fathom why a highly intelligent animal would essentially “bite the hand that feeds it.” I don’t come from animal activism and I knew very little about killer whales so I figured I was doing a documentary about a one-off; a single tragic event.

I was stunned by what I learned. For the next two years the information came in shockwaves.

I read Killer in the Pool by Tim Zimmermann and learned that Tilikum had killed twice before. I spoke to marine biologists, researchers, activists, and interviewed the former SeaWorld trainers, the folks who soon became the narrative voices of the film. All these folks taught me that there is tremendous social strife in these small tanks and that the animals fight all the time. In the wild, killer whales vie for dominance but the subdominant animal then flees the scene and the conflict subsides. In captivity no one gets to flee. They just keep fighting.

My team and I learned that family units are split up and calves are taken from mothers and moved to other parks. Eyewitnesses watched animals grieve, call out for each other and become traumatized.

Killer whales are accustomed to swimming up to 100 miles a day. At marine parks like SeaWorld, they’re left doing circles in small pools. They experience boredom, sickness, early deaths and they aggress, attacking and even killing human beings.

Even more astounding is that no killer whale has ever killed a human being in the wild. This has only happened in captivity. There is no documentation of a killer whale killing another killer whale or even seriously injuring another killer whale in the wild. This has only happened in captivity.

My producer Manny Oteyza and I would sit dumbfounded after these revelatory interviews, wondering whether we had heard it all, wondering if we were truly prepared to take on this massive story. Then we’d hear more. And more. To this day, multiple SeaWorld employees who have seen the film suggest to me that Blackfish barely scratches the surface.

I tried very hard to interview SeaWorld for the film. For six months we went back and forth. I tried former SeaWorld spokespeople as well, always imagining that SeaWorld’s voice would be represented in the film. I even provided them my list of questions (a documentary filmmaking taboo). They finally declined.

I’m told the members of SeaWorld’s upper management have seen Blackfish and have been bracing for impact all year. My secret and perhaps naïve wish was that they were already evolving. With their tremendous financial resources, I always hoped that they would join us in spearheading a movement that leaves behind animals for entertainment for good, and introduces sea sanctuaries. Since captive whales can’t be tossed back in the ocean (they don’t know how to hunt live fish, their teeth are destroyed from biting on metal gates, many are on antibiotics), the sea sanctuary alternative, where we cordon off an ocean cove with a net, would allow a killer whale to be fed by humans if necessary and would allow the animal’s health to be monitored.

A sea sanctuary is also a way for previously captive killer whales to live out their lives in a dignified, sustainable manner. It could be a profit-making enterprise. Who wouldn’t pay to go see a killer whale actually being a killer whale—something infinitely more gratifying than watching a killer whale do goofy tricks in a pool?

I think back on those times I watched killer whales at SeaWorld with my kids. I can’t help but think that maybe the reason we originally fell in love with the species is because we saw them up close. We saw these massive, intelligent animals gazing back at us. But this inevitably caused us to take more of them, to own them, to make them do tricks for us, and to master them. And now we see that this forty year mad-science experiment, where you put an apex predator in a pool and swim with it, didn’t work.

But I’m inspired by the reaction I’ve receive from folks who see Blackfish, especially the kids, the teenagers, and the young adults. They regularly ask me what they can do to make a change. They want to be the first generation to look back and say “I can’t believe people used to do this.” Because the most important lesson we learned from seeing killer whales in captivity is that they don’t belong in captivity.