A pool under your yard

I would make my friends have a fabulous photo shoot on it then just casually open it and cackle at their demise.

I'd have a "pool party" and invite all the people I hate...
Once they're all in the pool, it just takes the push of a button...
*Evil Grin*

Plants v.s. Zombies

Is this not dangerous? What happens when everybody gets out of the pool except 1 person, then you close it thinking everyone is out? That looks pretty thick, so it would probably be soundproof.

You can plan a perfect murder in there. No one can hear them scream when they start to drown..