Water polo leagues rank on points, but the system varies more than in most sports. Some use 3 for a win and 1 for a draw, some 2 and 1, and some do not allow draws at all and go straight to a penalty shoot-out, with points split between the shoot-out winner and loser. Check your league rules before you build the table.
Matches are four quarters, and goals for, goals against and goal difference are tracked the same way as in soccer. Scores in the teens are normal at a good level, so goal difference spreads out quickly over a season.