I know! What about...
...okay...
Hm... I don't think you can Politoed in episode 11... Unless you're using the Cheat Engine, or you go back to episode 9... But whatever...
Really, if you want things that work in the rain, i can suggest (Apart from Gyarados...)
Azumarill: In the Rain, that Aqua Jet is going to hurt... A LOT...
Vaporeon: That hydration can help a lot... Immune to all status aliment? Cool... The bad part is that Rest is not available yet...
Gastrodon: You know, while rain can help you, it can bite you in the ass... 100% Thunder... Well, Gastrodon doesn't take thunders and it's ability counters other water types... Good, good...
Luvdisc: That double speed... and it's all it has...
Ludicolo: Ludicolo is power - Neutral to ice beams and neutral to thunders, yeah... it's actually pretty good... The leech seed + Rain dish will keep you alive... Or just Swift Swim everything and sweep...
Politoed: Politoed itself is good in the rain... Do you how much a Hydro Pump hurts in the rain? A LOT!
Sorry for the lack of pokemon, but my memory is messed up and i don't remember all the water types available now... I can guarantee though, that most things that can learn a GOOD water move, will appreciate the rain...
The only reason rain is nerfed is because it doesn't last forever, but the power is the same... Just keep Politoed safe and have two pokemons with Rain Dance, to keep the rain going in any case...