The purpose of this work was to apply acoustic inversion to a bay in the Stockholm archipelago with strong variation of the bottom both vertically and horizontally. The inversions were based on measurements undertaken in May 200, of transmission loss over a 2.5 km long track. The bottom parameters were estimated by minimizing the difference between simulated and measured data. The parabolic wave equation was used as a wave propagation model and the inversions were carried out by a genetic algorithm. They resulted in a relatively good fit. The inverted bottom parameters were also evaluated by model predictions against a control data set of other frequencies than those of the inversion. The agreement between the estimated and measured parameters was good.