A Light-Ion-Beam (LIB) driven ICF reactor design with pressurized boiling water inside the target chamber is proposed, and several advantages and disadvantages of this concept are examined. For initial chamber pressures in the range of 5.106 – 1.4 · 107 Pa a density reduction of 1:100 in the vapor (steam) is required for adequate LIB propagation. This is achieved through the use of two consecutive laser pulses. Calculations of the laser energy required, the time histories of the physical properties inside the channels, and the effects of various radial energy deposition profiles are discussed. The results show that the required density reduction can be obtained with an energy requirement of 5–20 kJ/m/channel. A solution to the problem of cryogenic pellet injection in the high-pressure reactor environment is also suggested.