San Diegan Carrie Johnson was last in an eight-boat field Friday in a semifinal of the Summer Olympics' women's K1 200-meter sprint kayak race at the Eton Dorney Rowing Centre in Buckinghamshire, England.Johnson needed to finish at least sixth to qualify for Saturday's final. She was timed in 43.321 seconds, 1.042 seconds behind Yu Zhou of China, the sixth-place finisher. Lisa Carrington of New Zealand won in 40.528.The race was the last for the 28-year-old Johnson before she begins a four-year program at the UC Davis School of Veterinary Medicine on Monday.Johnson was sixth in her eight-boat first-round heat earlier today in 43.355. Johnson, who was born and raised in San Diego and graduated from UC San Diego in 2009 with a degree in biochemistry, was competing in her third Olympics.Johnson reached the semifinal of the K1 500-meter race Tuesday, was 10th in the K1 500 in the 2008 Games and reached the semifinals of both the K1 and K4 500-meter races in the 2004 Games.Johnson was introduced to kayaking through the San Diego Junior Lifeguard Program. She has been training at the Olympic Training Center in Chula Vista since 2002.Johnson was diagnosed in 2003 with Crohn's disease, which causes inflammation of the digestive system or gastrointestinal tract, leaving her unable to train that year."When people ask me what I enjoy most about my work at USA Canoe/Kayak, I say supporting an athlete like Carrie Johnson," CEO Joe Jacobi said."She upholds the spirit of the Olympic Games on and off the water and honors the sport with integrity. I have great respect for the challenges that Carrie overcomes every day to represent her country and her sport at the highest level."