Have alien civilizations built cosmic accelerators from black holes? Physics World.com

[bananas]

4. 100,000 ocean hydrophones, or lunar observation

While the oceans are far too murky for physicists to detect the light given off by the showers, Lacki reckons that the sound of a shower could be detected by a network of hydrophones in the water. However, because these neutrinos are expected to be extremely rare, he calculates that about 100,000 hydrophones would be needed to have a chance of detecting the neutrinos.

Whole of the Moon

Another possibility, albeit less sensitive, is to use the Moon as a neutrino detector. Indeed, the NuMoon experiment is currently using a ground-based radio telescope to try to detect showers created when 10^20 eV neutrinos smash into the lunar surface.