Under water sound serves as a very effective communication which can be made to vary in amplitude, frequency, and periodicity. These three variables are able to produce extremely wide and complex range of signals. Ambient noise and determination of its source is the biggest challenge in underwater acoustics industry. Yet ambient noise fields’ coherence is seen to be stable and hence can be utilized for determining seabed properties. Hydrophones in the form of vertical linear array at shallow depth of around 30m in the Arabian sea region are used for coherence estimation. To make better measurements of noise, it is preferred to avoid places where there is water movement relative to hydrophone array and cables. For various depths of hydrophones, the power spectrum and coherence plot of amplitude versus frequency are done and examined.