Salt Water. We already have muddy water, how about a salt water surf! The slugs around my garden inspired me to think of this. Basically it would be a water type move, but it would act as a grass type move whenever it hits a water/ground pokemon (ie slugs and amphibians which in real life can't tolerate salinity). It would also be super effective against slugma obviously who is another slug pokemon.
Thoughts? Other ideas?