Is water cooling necessary for high performance computers?

Water cooling is much better than it was 10 years ago. Back in 2004 and 2005 when the first end user water coolings were sold they were something like a high risk system. It was new, the tech was low tech and it was really water that was running inside the system. If you did something wrong, the house could be on fire.

Today things are different. Most water cooling systems are not water cooling but a liquid that cannot conduct electricity so if there's a leak, the computer won't be damaged, at least that's what they say.

But do you really such costly, high performance and expensive system to cooldown and 8 Core AMD or the latest Intel i7?

You don't.

If you like silence, air cooling is still the best you can install. I have one computer with liquid cooling. The temperature is perfect all the time and even with the air temp is at above 35 ou even 40ºC, the computer runs almost at 0ºC. Incredible. The problem is the noise. You almost can't hear music because the fans are running at peak speed all the time. The system does not come with software to control the maximum temperature or the fan speed/noise.

Air cooling, the best big fans, run much slower and they are capable of cooling even the fastest processors, for almost the same cost and with the advantage of being almost completely silent. Air cooling also has the advantage of lasting much longer in terms of lifetime and they don't require as much maintenance.

For mid performance computers liquid cooling is "out of question" simply because normal, even stock, air coolers are more than enough.