What is the absolute pressure 1.8 m below the surface of a lake?

Answer 1

You have to add the atmospheric pressure to the weight of the water above.

Take a 1m^2 column thru the water to the moon.
atmospheric pressure=101.3kpa=101.3N/m^2
water weight= density water*g*height= 1e3kg/m^3*9.8N/kg*1.8m=17.6kPa

absolute pressure= 17.6kPa+101.3kpa check my math.