Numerical modeling of the coastal ocean has progressed from first-order linear wave equations thirty years ago, to three-dimensional nonlinear numerical simulations today. The range of scales is vast, and the simulation problem presents many challenges. For the prediction problem, uncertainties in initial conditions and forcing motivate the consideration of forecast ensembles, which are widely used in operational numerical weather prediction systems. This in turn leads to consideration of the mechanisms of disturbance growth and instability in time-dependent fluid flows. In this context, a new method (due to recent COAS Ph.D. Christopher Wolfe) for obtaining multiple Lyapunov vectors for large systems is discussed.