I keep buying Riley new tennis balls because he always sneaks them outside and gets them muddy so they can't come back in the house. Right now I think the count is somewhere in the twenties. That being said if any one of those balls fall out of reach he goes insane and needs that ball. Today I was sleepy and my throw was a little short and one fell in the pool. After about half an hour of trying to avoid the water he jumped in after it. It was a valiant effort though.