Most watches are called waterproof but they’re really not waterproof. While most will keep water out if left untouched, if you try to engage the chronograph on most pieces the watch will become unstable and could let water in. Breitling has solved this problem by placing magnets on the pushers — the buttons, basically — and another magnet inside the movement. When you press the button, it engages the movement without actually touching anything — the magnets repel each other.
Sadly, this is a quartz piece. However, it is pretty beefy and since it’s really waterproof it might be good for divers with a few thousand bucks to spend.