Abstract— Channel coding is an essential requirement for digital communication systems, particularly for underwater acoustic channels, to perform accurately and reliably in the presence of ambient noise, absorption loss, interference, and much other impairment. Low complexity encoding and decoding algorithms are investigated i.e. order statistic decoding (OSD) of block codes for various modulation schemes and assumptions of underwater acoustic channel such as distance and multipath effects. These simple algorithms improve the bit error rate (BER) significantly unlike uncoded systems or other complex systems utilizing convolutional codes.