Sushi

1 ⅓ cups water ⅔ cup uncooked short-grain white rice 3 tablespoons rice vinegar 3 tablespoons white sugar 1 ½ teaspoons salt 4 sheets nori seaweed sheets ½ pound imitation crabmeat, flaked 1 avocado - peeled, pitted, and sliced ½ cucumber, peeled, cut into small strips 2 tablespoons pickled ginger