We report on our development of methods for acoustic underwater communication during 2004. The report is intended for telecommunication engineers or researchers within the area. The project has so far dealt with decision feedback equalizers, which is an effective and well known method for allowing high data rates in underwater channels. For covert communication we have earlier introduced turbo coding as a means to reduce the transmitted power. However, the progress in telecommunications is fast and new methods are emerging. To achieve even higher data rates or a more secure communication other methods, lying in the forefront of today´s telecommunication research, have to be used. We judge that the future underwater communication systems will be built around these methods. The present work has therefore been focused around studies and computer implementation of turbo (iterative) methods for equalisation and synchronisation and studies of MIMO-systems (MIMO, Multiple Input and Multiple Output). In the report, the turbo and MIMO methods are presented together with some proposals for systems with both single element and multi element transducer and hydrophone systems. We give a brief overview of these methods and outline a new method for turbo equalisation in MIMO-systems. A more detailed description and a theoretical basis for implementation of turbo equalisation and synchronisation is also presented. In the introduction we give a much less technical description-in-short of the work.