In this study we present a new formulation for the nonlinear wave-wave interaction source function in finite water depth. The formulation, denoted the reduced integration approximation (RIA), is shown to compare well with published formulations, both for shallow water wave-wave interactions <Herterich and Hasselmann, 1980; Polnikov, 1997; Hashimoto et al., 1998; A. Masuda and K. Komatsu, manuscript in preparation, 1998> and also for the asymptotic deep water limit: (1) the Hamiltonian formulation proposed by Lin and Perrie <1997>, by (2) Hasselmann and Hasselmann <1981>, and (3) the line integral transformation of Webb <1978> and Resio and Perrie <1991>. Of these deep water formulations, that of Lin-Perrie generalizing the Hamiltonian representation of Zakharov <1968> to finite depth water, is notable for its simplicity, efficiency and its ability to apply to very shallow water (kh≈0.3), and highly nonlinear (ϵ≤0.3) interactions. RIA is based on an analysis of the main resonance domain, which reduces the six-dimensional integration to a quasi-line integral to minimize computational time. In terms of computational time, RIA is a thousand times faster than the EXACT-NL version formulated by Hasselmann and Hasselmann <1981>, with similar accuracy. Thus RIA can be considered a candidate for operational forecasting in finite depth water, in the sense that the discrete interaction approximation was presented as a candidate for operational deep water wave forecasting by Hasselmann et al. <1988>. ¿ 1999 American Geophysical Union