  We investigate the zero-temperature properties of a diluted homogeneous Bose
gas made of $N$ particles interacting via a two-body square-well potential by
perfor ming Monte Carlo simulations. We tune the interaction strength to
achieve arbitrary positive values of the scattering length and compute by Monte
Carlo quadrature the energy per particle $E/N$ and the condensate fraction
$N_0/N$ of this system by using a Jastrow ansatz for the many-body wave
function which avoids the formation of the self-bound ground-state and
describes instead a (metastable) gaseous state with uniform den sity. In the
unitarity limit, where the scattering length diverges while the range of the
inter-atomic potential is much smaller than the average distance between atoms,
we find a finite energy per particle ($E/N=0.70\ \hbar^2(6\pi^2n)^{2/3}/2m$,
with $n$ th e number density) and a quite large condensate fraction
($N_0/N=0.83$).
