Several methods for computing the non-linear energy transfer due to resonant wave-wave interactions are implemented in an experimental version of the SWAN wave model. These methods and their mutual relationships (illustrating their evolution from one to the other) are described. Of these methods, two are addressed in some detail. Of the first, an approximate method called the modified SRIAM method, the accuracy and efficiency are numerically demonstrated for various directional spectra. The second, an exact method called the FD-RIAM, is up-graded from an earlier version (Hashimoto et al., 1998) on the basis of Komatsu and Masuda (2000) to solve an instability problem caused by singularities in the Boltzmann integral. The accuracy and stability of this exact method too are numerically investigated. This FD-RIAM, supplemented with all other processes of generation and dissipation (and triad wave-wave interactions) in SWAN, is applied to the shallow water Lake George in Australia.