A sharp interface method to capture the exact dynamics of liquid - vapor interfaces, has been developed. The two-dimensional, unsteady Navier-Stokes equations are solved using a standard finite-difference formulation on a fixed Cartesian grid, while the interface is tracked dynamically using a linear front tracking method that utilizes marker particles. To capture the exact physics of the interface, a sharp interface technique is used, where all interfacial and material properties like surface tension, density and viscosity are directly evaluated based on the exact location of the interface. In addition, to enforce the appropriate boundary conditions for the pressure, a special variable coefficient pressure Poisson solver with modified coefficients has been developed. Single and multiple vapor bubbles rising through a quiescent liquid, are simulated. Bubble merger and fracture processes are also investigated. The proposed method was not only found to be more accurate, but also more efficient when compared diffused-interface methods.