The photodissociation cross section of water in the first absorption band naturally splits into two parts, a rather dominant and broad background, and a series of isolated resonances. We focus here on the semiclassical calculation of the background term. We compare various semiclassical methods of calculation, including the reflection approximation, the Wigner-Weyl series, Airy function approximations, and higher-order approximations in the time domain, and find that only the latter gives quantitative agreement. They are numerically efficient as they can be reduced to a 2-D spatial integration together with a Fourier transform.