Efficient communication through acoustic underwater channels is studied. Particularly, the paper addresses how turbo equalisation can be combined with soft iterative channel estimation to achieve error-free decoding of long-range underwater transmissions. We also discuss exploitation of multiple transceivers can be used to increase the performance of underwater communication systems. The prime focus of on-going work is to study the characteristics of the channel and to evaluate the performance of the proposed techniques. For these purposes, real data, collected in the Baltic Sea, are used. In an initial investigation a bit rate of 8 kb/s, including the turbo code, corresponding to 2.58 kb/s of information bits, error-free transmission over a distance of 30 km was accomplished.