You can do that with non-conductive fluid on pretty much any computer. Well, at least not an HDD.

You can see that this person has their entire motherboard components submerged in mineral oil.

Even with "waterproof miners" I wouldn't even begin to fuck around and put any of my electronics in water. I have messed around with watercooled CPU/GPU setups and know just how easily a minor leak can occur even with the most meticulous setup. I don't want to trust some manufacturer properly waterproofed the system. If the system is simply coated with a water proof solution then I would be worried about somehow scratching the solution or if it was properly applied. If the system is somehow enclosed in a waterproof case I would be even more worried about how properly sealed it is. Also, water is simply not good for metal. Water has other elements in it. Some water is harder than others. Those calcium deposits and build ups around your shower head? Yea I don't know if that is necessary an ideal environment to put your components in. Also, water isn't as good of a conductor of heat as oil is. The oil is also non-conductive so any mistakes, leaks, scratches of the material wouldn't result in a brick.