For H2O use HF/6-31G* to optimize the geometry and then calculate the ESP charges according to each of the methods Merz-Singh-Kollman, CHELP, and CHELPG, To do this in Gaussian, in addition to Opt on the line beginning with a #, one includes Pop=MK or Pop=CHELP, or Pop=CHELPG. If you are using the online WebMO Demo, after you get the optimized-geometry model using Gaussian, click on New Job Using This Geometry, click the right arrow, choose Gaussian, click the right arrow, then choose Other as the Calculation, and enter Pop=MK in the Enter Calculation window, click OK, and click the right arrow. Scroll down in the output model display to see the ESP charges. Compare with the Mulliken charges, which are listed as the Partial Charges by WebMO. If you have Spartan Student, after you optimize the geometry, go to the Model menu and choose Ball and Spoke; choose Configure on the Model menu, click Electrostatic Charge, click OK, and click Labels on the Model menu. Only one kind of ESP charge is given by Spartan Student.