  Baryon number violation appears in many contexts. It is a requirement for
baryogenesis and is a consequence of Grand Unified Theories (GUTs), which
predict nucleon decay. Nucleon decay searches provide the most direct way to
test baryon number conservation and also serve as a unique probe of GUT scale
physics around $10^{14-16}$ GeV. Such energies cannot be reached directly by
accelerators. However, they can be explored indirectly at large underground
water Cherenkov (WC) experiments, which due to the size of their fiducial
volume are highly sensitive to nucleon decays. We review searches for baryon
number violating processes at the state of the art WC detector, the
Super-Kamiokande. Analyses of the typically dominant non-SUSY and SUSY nucleon
decay channels such as $p \rightarrow (e^+, \mu^+) \pi^0$ and $p \rightarrow
\nu K^+$, as well as more exotic searches, will be discussed. Presented studies
set the world's best limits, which circumvent the allowed parameter space of
theoretical models
