|Patrat||Normal||Tall/Shaking grass||50%, 100% (Shaking grass)|
|Red Basculin||Water||Surf/Super Rod (after Gym 5)||100% (Surf), 30% (Fishing)|
|Blue Basculin||Water||Surf/Super Rod (after Gym 5)||100% (Surf), 30% (Fishing)|
|Poliwag||Water||Super Rod (post-game)||70%, 65% (Rippling water)|
|Politoed||Water||Super Rod (post-game)||5% (Rippling water)|
You're now in Route 19, an extremely short area. Move forward and talk to Bianca. She gives you the obligatory explanation of how tall grass works and a run-through of how to catch a Pokemon. Once done, she'll simply leave and allow you to get on with things.
Follow the path provided, moving through the first patch of grass and halfway around the second patch. Move through the rest of it, ignoring the girl wandering around in it. You'll now be south of an area that contains a Youngster and an item amidst a bunch of grass. Go up and collect the item, which turns out to be a Potion .
You can talk to the Youngster and find out how to jump over ledges by answering 'No' to his question. In this route there are only two Pokemon that can be caught (when you first begin anyway), Patrat and Purrloin, both of which you should catch. You may then want to train up your new Pokemon up to a decent level.
Staying around the end of the route whilst training and catching Pokemon is the most efficient way to do it, as the Pokemon Center in the next town is very close, so you can easily heal your Pokemon there.
Other than that, the only thing left to do is continue on to Floccesy Town. Just before you reach it, a man with fiery hair will stop you and commence a conversation. He is Alder, the former Pokemon Champion during Pokemon Black & White. Once done, continue and enter the town.