Pressure measurements made in two turbid natural waters have led to the inference that the effective depthmean in situ density values, rho sub(eff), of these waters are less than (approx equal to 0.4%-4.5%) that of the density of the same water after removal of suspended sediment. The values of rho sub(eff) in a given site differed from one tidal cycle to another (approx equal to 1.9%). These values varied slightly (less than 0.8%) from midtide to slack water period of the same tidal cycle, with rho sub(eff) being lower at midtide. It was found that the use of bulk density to estimate tidal elevation yielded an understimation of tidal range (up to 7%). The underestimation has been corrected (to within plus or minus 1.5%) with the use of rho sub(eff) parameter. For clear waters there was no measureable understimation in tidal range. The observations indicate an apparent in situ density reduction for turbid natural waters. With the use of two pressure transducers at a known vertical separation, the value of rho sub(eff) over this vertical column of water may be determined during each sampling of pressure values. The present studies indicate that when pressure transducres are used for water level measurements in turbid natural waters, the use of rho sub(eff) in contrast to the bulk density, significantly improves the measurement accuracy. For celar waters, precision density measurements made on discrete water samples agreed with rho sub(eff) values derived from pressure measurements to better than plus or minus 0.4%. Thus, use of rho sub(eff) is expected to improve the accuracy of water level measurements also from clear water estuaries where depth-mean water density undergoes marginal changes with differing phases of tide and significant changes with seasons