The first stand up jet ski was created in 1973 by Kawasaki called the JS 400, which had a twin cylinder two stroke engine. Stand up jet skis became popular due to advantages like being good for racing similar to dirt bikes due to balance requirements, lower risk of injury compared to sit down jet skis, and their use in freestyle competitions which now require backflips. Modern stand up jet skis have evolved significantly from 36 years ago, with lighter designs, larger engines up to 1200cc compared to 650cc in earlier models, and a more sleek futuristic look while maintaining the basic shape of early models.