  An analytical description of the interface motion of a collapsing
nanometer-sized spherical cavity in water is presented by a modification of the
Rayleigh-Plesset equation in conjunction with explicit solvent molecular
dynamics simulations. Quantitative agreement is found between the two
approaches for the time-dependent cavity radius $R(t)$ at different solvent
conditions while in the continuum picture the solvent viscosity has to be
corrected for curvature effects. The typical magnitude of the interface or
collapse velocity is found to be given by the ratio of surface tension and
fluid viscosity, $v\simeq\gamma/\eta$, while the curvature correction
accelerates collapse dynamics on length scales below the equilibrium crossover
scales ($\sim$1nm). The study offers a starting point for an efficient implicit
modeling of water dynamics in aqueous nanoassembly and protein systems in
nonequilibrium.
