Accurate assessment of site-specific water level, phase difference, magnitude, and direction of tidal constituents is critical to understanding tidal behavior of deep-sea and estuarine environments. It is also an indispensable requirement for planning and safe execution of coastal infrastructures and optimal movement of water vessels. These assessments are usually based on tidal harmonic analysis, which is a mathematical method of extracting sinusoidal components of specific frequencies from e.g., water level/tide gauge records. The conventional modus operandi is the Least Squares Method whose accuracy largely depends on the length and quality of time series data. The University of Hawaii Sea Level Center in collaboration with the National Oceanographic Data Center provides research quality water level data on over 250 stations all over the world of which 7 lies at the head of the Bay of Bengal. These data supplemented by recent tide gauge records sourced from Bangladesh Water Development Board (BWDB) and Bangladesh Inland Water Transport Authority (BIWTA) are used in this study. The points of interest are Chittagong, Teknaf, Angtihara, Khepupara, and Tajumuddin which cover the Eastern, Central, and Western Estuarine Systems (EES, CES, and WES). The study would identify the modulation of major harmonic constituents (M2, S2, N2. K1, O1, S4, M4, M6, MS4) resulting from the seasonal effect of meteorological forcing and non-linear shallow water interaction over the estuarine river system. In addition, the study aims to classify the above stations based on sub-tidal signatures in recorded water levels.