Pressure P = WH where W = the specific weight and H is the depth of the water
N = Newtons and m = meters
The specific weight of water is 9800 N/m3 So if the depth of the water is .3 m and you want the pressure at the bottom of this .3 m depth,
P = 9800 (N/m3)*(.3m) = 2940 N/m2