BEIJING-The Water Cube is the perfect habitat for Michael Phelps, who truly must be some sort of amphibious creature.

How else to explain the way he swamped the field, and his world record in the 400 individual medley on Sunday morning?

Phelps began his quest for eight gold medals at the 2008 Olympics with a smooth victory in the race that was supposed to be his toughest.

Phelps felt sluggish at dawn, warming up at the Athletes' Village pool, where he begged his coach to let the Beijing 400 IM be his last. He doesn't want to suffer through the pain of it anymore.

But once he got to the Cube, his skin began to tingle.

The Cube's walls are made of translucent, glowing bubbles, which change color at night. Inside, the surrounding membrane makes you feel like you've been swallowed by a gooey organism. Even if you're not in the water, the whole place has a liquid, psychedelic aura.

If you're in the pool, staring upward, the ceiling looks like it's made of fish scales.

For all we know, the Cube is floating around under the microscope of a gigantic alien, who follows Phelps' movements with curiosity and awe.

Phelps doesn't swim through water the way normal humans do. He commands it. With his large hands, he sculpts it. With his size 14 flippers, he parts it. On the underwater camera shots, he really looks like a dolphin, his legs undulating and his long torso generating torque. On the surface, he's a bug who skims along, meeting no resistance.

He is Michael Phelps, the greatest swimmer of all time, a marvel of biomechanics, physiology and concentration.

Not to mention sheer will. Phelps, 23, has been swimming since he was 6 years old. Despite all his accomplishments, he keeps working, hour after cold, chlorinated hour, focused on that black line. He keeps getting better. He set his 25th world record Sunday. We will see more this week.

His goal of breaking Mark Spitz's 36-year-old record and winning eight gold medals in one Olympics once seemed outlandish, something a cartoon character would declare. But after the 400 IM, he must feel confident that even in the relays he can make up any lost ground.

The race was close through the first half, with Ryan Lochte and Laszlo Cseh challenging in lanes 5 and 6. Then Phelps zoomed away to a final time of 4:03.84, lowering his record by 1.41 seconds.

He followed his plan of finishing under 4:04. Phelps has an uncanny knack for hitting his times. After countless workout laps and races, the clock in his head never fails.

Phelps was on world-record pace until midway through the backstroke leg, when teammate Lochte pulled ahead by a swimming cap, briefly. Phelps reeled him in with his much-improved breaststroke and was 1.40 seconds ahead of his record and a body length ahead of Lochte after six laps.

The freestyle leg was Phelps in motor mode, gaining two body lengths on Lochte, who has challenged Phelps in the past, but faded fast to third place. Hungary's Cseh was second. Lochte, the Florida Gator from Daytona Beach, said he went out to fast and spent himself on the backstroke leg.

Phelps felt tired before the race. For the first time, Olympic finals are being held in the morning to accommodate NBC's prime-time broadcast in the United States. (They paid for it. They get what they want, when they want it.)

But Phelps, a notoriously miserable loser, got his game face on.

"To be honest, I didn't really feel that great," he said. "Then going into the ready room I started getting these chills up my body. And right then and there I knew I was starting to get more and more excited."

After Phelps hit the wall and checked his time, he pulled off his goggles and scanned the crowd. His eyes met those of President George W. Bush, who was in the stands.

"He nodded and waved the American flag so that's a pretty special feeling," Phelps said. "I waved and nodded back and it was neat to have the president here and have him cheering us all on."

Phelps' lips quivered on the medal podium as "The Star-Spangled Banner" played (and cut off abruptly after "land of the free").

"I wanted to sing, but I couldn't stop crying," Phelps said.

His progress will define the first week of these Games, and, possibly, these Olympics. He's got a long way to go: The 4x100 free relay, the 200 free, 200 fly, 4x200 relay, 200 IM, 100 fly and 4x100 medley relay.

As Phelps' coach, Bob Bowman says, "With Michael, everything is possible, nothing is absurd."

Eight golds? Why not? Here at the Cube, Phelps' wet home away from home, he keeps getting better.