Factual error: In the very first scene a giant squid swims past Fujimoto. It swims in the wrong direction however, with its tentacles in front. In reality squid swim backwards.
Factual error: Sosuke rescues Ponyo from the sea, and then puts her in a bucket of tap water. Fresh water would kill a saltwater fish.
Factual error: Ponyo is found in the sea, but goldfish are freshwater fish.
