1. Combine water and rice in a saucepan and bring to a boil. Cover, reduce the heat to low, and simmer until rice is tender and water has been absorbed, about 20 minutes. Remove from the heat, stir in vinegar and salt, and set aside to cool for at least 5 minutes.

2. Cover a bamboo sushi mat with plastic wrap to keep rice from sticking. Place one nori sheet over the plastic. Spread rice evenly onto nori sheet, leaving about a 1/2 inch uncovered at the bottom. Arrange cucumber and avocado across the center of the rice. Lift the mat, roll over cucumber and avocado once, and press down. Unroll, then roll again towards the uncovered end of the nori to make a long roll. Seal roll with a little water if necessary. Repeat to make remaining rolls.

3. Use a sharp, wet knife to slice each roll into 6 pieces.

Tips

You can add either fake crab to keep the sushi rolls vegetarian or smoked salmon if you prefer.