Olympic Swimming Results 2012: Biggest Shocks from Early Races

The 2012 London Olympics have just started, but there's already been plenty of drama in the pool.

The greatest swimmer in history stumbled in his first race, a gold medal favorite nearly had his dreams shattered by some poor officiating and a women's world-record holder barely qualified for the finals in her best event.

Here are the details on the biggest shocks from the early action in London.

Michael Phelps Squeaks Into the 400-Meter Individual Medley Finals

Michael Phelps is unquestionably the best swimmer in Olympic history, and after setting the world record in the 400-Meter Individual Medley in Beijing, he seemed like a lock to finish in the top-two in London.

However, Phelps almost had Saturday night off, as he barely qualified for the finals. He finished with a time of 4:13.33 to secure the eighth and final spot. He beat out Laszlo Cseh of Hungary by just seven-hundredths of a second, narrowly avoiding disaster in his first race of the 2012 Games.

Phelps was spared some embarrassment by qualifying, but if he doesn't improve in today's finals (2:30 p.m. ET), it will be one of the biggest disappointments in the American's illustrious career.

Park Tae-Hwan Disqualified, Then Reinstated in 400-Meter Freestyle

Phelps wasn't the only big name who almost missed out on Saturday night's competition.

South Korean star Park Tae-Hwan, the defending gold medalist in the 400-Meter Freestyle, was initially disqualified for the finals after being flagged for a false start in the prelims. Although he won the heat with a fantastic time of 3:46.68, it appeared he would be denied a chance to defend his gold.

Luckily, Tae-Hwan won his appeal, as it was decided that the movement came from Australian Dave McKeon in lane three.

Tae-Hwan is now the favorite for the finals yet again, which will take place at 2:51 p.m. ET on Saturday.

Stephanie Rice Almost Misses Out on Women's 400-IM Finals

Like Phelps, Stephanie Rice set a world record in the 400-Meter Individual Medley in Beijing. Also like Phelps, she barely qualified for the finals in this year's event.

The Australian finished seventh in qualifying, finishing with a time of 4:35.76. She was more than four seconds slower than American Elizabeth Beisel, who finished in first with a time of 4:31.68.

The 24-year-old should still be considered a favorite in Saturday's finals (1:11 p.m. ET), but she will definitely need to improve on her prelim performance.