An algebraic Hamiltonian for H2O, D2O, H2S, CH2 of CH2Br2 and CD2 of CD2Br2 containing anharmonicities and resonances is proposed with coefficients elucidated from the fit with the experimentally observed levels. It is demonstrated that most often the anharmonic parts show clues of action (energy) localization. Resonances are shown full of periodic, quasiperiodic and chaotic motion, while the intersection of the various resonances is full of chaotic motion. The barrier in intramolecular vibrational relaxation with extreme mutual irrational ratios of resonance frequencies is shown full of periodic or quasiperiodic motion, leading to the dynamical bottlenecks.