Actually, a lot of pokemon who don't need to be in the water can learn splash:

Grumpig/Spoink
Azurill
Hoppip/Skiploom/Jumpluff
Wynaut
Cleffa/Clefairy/Clefable
Delibird
Poliwag/Whirl/Wrath/Toed

now, some of those non fish pokes could pull a could rouse if in the water, but I think seeing a Clefable, or Wynaut splashing on the ground would confuse the crud out of a pokemon fighting it, I mean, what would you think about seeing it, you would be distracted/laughing/confused by it.