Pixar consulted real marine biologists, but artistic license took precedence. Here’s the reality check:
It wasn't a cloud passing over the sun. It was a shadow, massive and silent. A barracuda. It moved like a missile, eyes locked on the reef. Marlin tried to fight, tried to protect his family, but the tail strike sent him tumbling backward into the anemone, the world spinning into unconsciousness. finding nemo
"Dad!" he cried, but the world was suddenly full of air and blinding light. Pixar consulted real marine biologists, but artistic license