Ash and Misty each catch a Seaking as part of a Seaking Catching Competition (They are later returned to the lake; off-screen in the case of Ash), Misty's Poliwhirl is revealed to know Mega Punch, Misty wins the Seaking Catching Competition.
During their trip to Ecruteak City, Ash and co. encounter a Poliwrath and it's trainer, a young boy named Andreas, who are training for a Seaking Catching Competition. After Andreas talks smack about Misty's Poliwhirl She decides to enter the competition to show him who's boss. Who will win this Seaking Catching Competition? and Which is better: Poliwhirl or Poliwrath?
Bass and Catfish are mentioned by Ash in this episode.
Andreas says that if Misty's Poliwhirl was any good it would have evolved by now. But the decision to evolve a Poliwhirl is down to the trainer as this can only happen by use of a Water Stone. Andreas should know this as he has a Poliwrath and must have used a Water Stone at some point.