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Approximately 71% of our planet is covered with oceans. It is also known that oceans are the last frontiers for the mankind's survival and therefore it becomes pertinent that they are studied in great details. It has been found that the exploration of the oceans can be done more precisely using acoustics as one of the methods, as the acoustic waves can propagate over large distances and also using a broad spectrum of frequencies various issues of the ocean studies can be addressed more effectively than many of the other methods, both in terms resolution (using high frequency components) of measuring parameters and over large ranges (using low to very low frequency components). Currently with the technological advancement and improved computing algorithms, we have state of art systems for ocean exploration, which can provide information about the sea floor, sub-surface including ocean floor classification. These could be projected in 2-D and 3-D visualization to a great accuracy. Also available are acoustical methods wherein one can obtain an extremely important information about water column properties (both in terms of bioinformation and physical properties), and has great importance as this water column is the medium for transmission of all kind of energies(acoustic for short, medium and long ranges and some time light source for exploration over a very short distance) that are used for exploration on the oceans. It will therefore be interesting to understand the progress of underwater acoustics from its very primitive stage, where acoustic transmission through water medium was used for first time to the present day highly complex but very advanced acoustic sea-floor surveying systems. It will also be interesting to know, with a very old maritime history of using seas for transportation, as to what were the methods used by early time seafarers to understand depths of the oceans they were sailing. It has taken almost a century in developing an acoustic system to arrive at the present day advancement. An attempt has been made to present a perspective of evolution and advancement in underwater acoustics and related electronic, material and computational advancement, starting from the early attempts to the modern day acoustic equipments

Data collection for logical interpretation of the observations made in any branch of science is solely dependent on the method or an approach to a particular problem. The techniques therefore followed to obtain complete or near complete solution depend upon the type of instrument used to make these observations. A morphological observation method to understand the sea floor involves a complex set of data collection to arrive at proper interpretation of a morphological feature. In the marine environment, careful system design is essential to overcome errors due to unstable nature of observation platform and the medium, which undergoes a continuous process of random or periodic variations. The ultimate goal of a bathymetric survey is to produce a bathymetric map of an area surveyed with a certain geographical reference frame.[1] The other important aspect of bathymetric observations is for geological and geophysical exploratory type of surveys, which provide a vital link between studying morphological variations of the sea-floor and their impact on drawing inference on tectonic changes as a primary evidence of the earth-ocean dynamics. This data can provide a great insight in earth evolutionary processes on continental shelf dynamics, canyon and sea-mount formations, riverine fans extending to large distances into ocean basins. Bathymetry data obtained for any area is very useful in gravity anomaly studies etc. In all these observations, a good navigation system plays a key role of fixing a proper geographical reference frame. This will need a specific knowledge of the medium, underwater acoustics and a number of complementary sensor data such as attitude and heave measurement in addition to a number of instruments available for the depth determination. A sub-bottom profiler basically provides details of the substrata layering of the ocean floor. During the movement of terrestrial material through rivers and flows meeting the sea, gets deposited in the nearshore region initially. This deposited material in the form sand, clay or silt OR in a combination, moves towards the deeper ocean floor due to wave interaction and bottom currents. As new deposits keep accumulating, layers of these deposit are formed. In many cases, organic matter also gets entrapped with this material. At certain conditions of pressure (due to sediment mass) and temperature, this organic matter converts into hydrocarbon deposits or gas-hydrate deposit. Therefore the study of the substrata below the sea-bottom provides in-depth knowledge of possible hydrocarbon deposits. These layers also provide history of bottom evolution. Also with these sediments foraminifera species which die, get deposited. These species provide vital information about the climate in the past. An altogether new branch of oceanography termed as ?paleo-oceanography? has evolved. Therefore the subbottom profilers are an important sonar tool in ocean exploration.