You're fishing with Lana at Brooklet Hill, trying to catch some new Water-type Pokémon.

Lana feels a tug at her rod and she pulls it up. All that comes up is another Magikarp, the 4th one...

"How unfortunate. I didn't catch a strapping young swimmer on my hook..."

"You know, once I caught a Wailord out at sea. I did it all by myself. Do you believe that?"

She enjoys telling false little stories like that, especially since you tend to fall for them.