  We report the results of a search for neutrino-induced particle cascades
using a deep ocean water Cherenkov detector. The effective mass of the
detector, a string of seven 40 cm diameter photomultipliers at 5.2 m spacing,
is found through simulation analysis to be surprisingly large: greater than 1
megaton of water at incident neutrino energies of 1 PeV. We find no evidence
for neutrino-induced cascades in 18.6 hours of observation. Although the limit
implied by this observation is the strongest yet for predictions of active
galatic nuclei (AGN) neutrinos at energies above 100 TeV, perhaps the more
intriguing result is that the power of these techniques can be exploited to
test these AGN models in a relatively short time.
