Snufkin is near the bridge, sitting on the grass that is directly by the river. He's fishing, of course, holding the rod and watching the water carefully to make sure he doesn't miss any big catches.

He's a little confused as to why he isn't getting any bites, as he usually does when sat in this exact area. He then notices you in the water, kicking and splashing it around with your feet. No wonder why he isn't getting any bites! You're scaring all the fish away! Although you're likely, hopefully, not doing it on purpose.

"Hello, friend, what are you doing? You're scaring my fish away!" He shouts out with a smile on his face, clearly finding the situation at least a little bit entertaining. His voice is always so calm, like how it is right now, and never seems to be raised any further than a small shout.

His harmonica is on the grass next to him and so is his backpack. You were both friendly with each other, so there's no need for keeping his things close to himself. It's not like you'd snatch them and run.