Ultraviolet radiation is one of the principal forms of energy which is dissipated from an electrical discharge in water. For a stored capacitor energy of 1500 J, up to 28% or 420 J has been converted to uv radiation with a peak radiant power of 200 MW. Of the energy transferred to the plasma, 36% was converted to radiation. The efficiency of radiation was maximum for a length of the discharge channel of approximately 3.8 cm. Scaling rules are given.