yes you find this on the floor of a cave don't ask questions
I can see what they were doing here. They wanted to make another no-weakness Pokemon, aside from Ghost/Dark, so they took a type with a sole weakness, and gave it an ability that negates that weakness. But I think it's a little strange, since Tynamo and its ilk are obviously lamprey-eel things, and ought to be Water/Electric.
But that's an entirely different Pokemon right there. It would have Water STAB, and require some sort of new bullshit ability to negate THREE weaknesses. So maybe it's for the best that they just ignored the fishy part of it, when deciding type.
Also, you notice how every single swimming Pokemon has Levitate? I mean, you throw out a Goldeen, and the thing just hovers there. Shouldn't you only be able to use those kinds of Pokemon in the water, or at least have to throw out a pool of water or something? GAME IN WHICH YOU CAPTURE MONSTERS IN TINY BALLS AND THEN MAKE THEM SHOOT LIGHTNING AND FIRE AT EACH OTHER, I BEGIND TO DOUBT YOUR VERISIMILITUDE.
Tynamo's design doesn't really do anything for me, but I like how the electricity pulses along its side. That's neat-o.