Combine the water and rice in a saucepan and bring to a boil. Cover, reduce heat to low and simmer for 20 minutes, or until rice is tender and water has been absorbed.
Remove from the heat and stir in the vinegar and a pinch of salt. Set aside to cool.
Cover a bamboo sushi mat with plastic wrap to keep the rice from sticking. Place a sheet of seaweed over the plastic.
Spread rice evenly leaving a little space of seaweed at the bottom.
Arrange strips of cucumber across the center of the rice.
Lift the mat and roll over the vegetables once and press down.
Unroll, then roll again towards the exposed end of the seaweed sheet to make a long roll. Wet with little water if needed.
Use a sharp wet knife to slice the rolls into 5 or 6 slices. Serve cut side up with your favorite sushi condiments.