An explicit solution is given to the one-dimensional hydrodynamic shock tube problem. The dynamic and thermodynamic quantities in the quasisteady states and the properties of the resulting waves are derived from the diaphragm pressure ratio and the initial conditions of the driver gas and the driven liquid. The planar flow results also apply, at the instant of diaphragm rupture, to the equivalent problem in a cylindrical or a spherical geometry, such as an underwater blast for example, and are therefore useful for establishing the initial blast properties. For this reason, some preliminary experimental data on low-energy, spherical underwater explosions are included.