  The Peregrine breather, today widely regarded as a prototype for
spatio-temporally localized rogue waves on the ocean caused by nonlinear
focusing, is analyzed by direct numerical simulations based on two-phase
Navier-Stokes equations. A finite-volume approach with a volume of fluid method
is applied to study the Peregrine breather dynamics up to the initial stages of
wave breaking. The comparison of the numerical results with laboratory
experiments to validate the numerical approach shows very good agreement and
suggests that the chosen method is an effective tool to study modulation
instability and breather dynamics in water waves with high accuracy even up to
the onset of wave breaking. The numerical results also indicate some previously
unnoticed characteristics of the flow fields below the water surface of
breathers, which might be of significance for short-term prediction of rogue
waves. Recurrent wave breaking is also observed.
