For the Whomping Willow, you scored a brilliant 17! You're able to speak with the plant and it lets out a strained sort of conversation with you. There's things that it seems to be abjectly refusing to say, as if it's under some sort of enchantment- especially when or if Zelda tries asking what its purpose is, or why it's particularly violent when things approach. We rolled an arcana check for you on that, since we figured you might be interested in knowing, and congrats! You got a 12 (including a +2 modifier because, again, smart-) and you'll be able to figure out that the way it's kept alive is by proceeding very carefully with some sort of sentient oath it's made to its enchanter.

You don't know what enchanted it to begin with or how it came to be, but you also know that you can't calm it down by simply asking it to. It's design is very much a "hurt on sight" sort of thing, which is unfortunate. The Whomping Willow is actually rather quite nice aside from the stabby thing.

On the lake front (heh)- you rolled a 2. That's not going to get you much, unfortunately. Zelda can see that there's water there, but she can barely seem to keep much of her senses focused on any one thing for very long. It's frustrating, but there just seems to be nothing more explicit to find.