1. I was in my hot tub the other day. A small computer speaker fell off the shelf into the hot tub it was plugged into the wall. Why am I not dead?

2. I have a truck winch that I want to use in my garage. It's 12v, meant to hook up to a car battery. A quick Google search for 120 to 12 converters brings up a bunch of them that specifically say they're for lighting. Will those work for powering my 12v winch?

#1. A number of reasons... culminating in the fact you didn't get current passing through your heart to stop it. Might not be so lucky next time.

#2. Won't work for the same reason you can't start your car with a computer laptop A/C adapter... not enough current.

So the follow up then is, what do I have to buy to be able to operate that winch off an indoor outlet?

So the follow up then is, what do I have to buy to be able to operate that winch off of an indoor outlet?

You don't. You buy a winch intended for 110v. The booster charger you would need to do that would cost several hundred dollars to provide enough current. The kind you jump start Tractor Trailer trucks with.

Get a deep cycle battery and a float charger to keep the battery charged between uses to run it otherwise.