Yeah, but if you think again we can just leave it that the hero gets under these reeds, noone will mind if it doesnt move like a grass patch I gues, we just have to give it the normal water behavior byte to make water pokemon appear, since I'm sure were not able to make extra pokemon appear in grass/reeds/and water but the idea youve got is nice.
and if someone really minds it really that it isnt a grass byte we can just animate it :>