Let's Make an Offer

I was at a job interview and the interviewer gave me two logic puzzles. I'll repeat them:

1. You are on a boat in a lake. You have, in the boat with you, a rock. You throw the rock into the water, it sinks. What happens to the water level on the shore?
   
2. The classic "Let's Make a Deal" paradox: Suppose you're on a game show and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?
   

Any takers? Assuming you haven't seen them already, of course.