FANTASTIC !!!!
It's so funny! The battle will never end, it's just reapeating the same things over again. It's normal since using Splash attack can't end a battle.
Wait... there's something wrong, I'm sure you didn't think about it. The Splash move have 40 PP, that means you won't be able to use that move when you already used it 40 times. When a Pokémon no longer have any PP for all of its moves, it automatically uses the move Struggle, this attack is 1.5 times stronger than Tackle but the user takes 1/4 the damage. So yes, basically, you can win with a splashing Magikarp. You forgot about this huh?
Anyway, it doesn't mean it's not good! I'm adding it to my favorites and I'll show it to all my friends!