How to thoroughly waterproof a Macbook?
I'm going to stick my neck and say that you cannot do this.  No matter what materials you have to hand, your MacBook requires open access to the internals via vents and grills etc for fans to push unwanted air out, or suck cooler air in etc.  You can't safely just block all this up.  You can get a wide range of keyboard covers to allow you to type with wet/dirty hands etc, but protecting the entire unit isn't really practical at all. Servers are amenable to being bathed in mineral oil but that requires special cabling, removal of all blowers and potentially modifying the heat sink depending on the specifics of the CPU and coolant temperatures.


http://www.grcooling.com
http://www.tomshardware.com/news/Server-Cooling-Hardware-mineral-oil,17348.html