The aim of this paper is to study a way to overcome the problem of multipath distorsion in acoustic underwater communications by using a time-reversal mirror (TRM). A set of experiments is presented using a TRM made of 64 reversible transducers and different results will be emphasized. One result is related to the high focusing property obtained with a TRM operating in a bounded channel. It will be shown that the time-reversed beam is much thinner than the one observed in an unbounded fluid. The second result is the time compression observed for the time-reversed acoustic multipath pulse. The influence of the number of elements of the TRM on the focusing and on the time compression is discussed.