18-time Olympic gold medalist Phelps is all set to plunge back in.

Michael Phelps has officially announced his competitive return to the sport, for the first time since 2012. Come Thursday, he will be seen at the Mesa Grand Prix, seeded on top, in the 100-metre butterfly race.

The 18-time Olympic gold medalist will test his speed on Friday in the 50-metre freestyle, apart from the 100 butterfly. The 28-year-old looked relaxed and positive, talking about his comeback after 628 days.

"I am looking forward to wherever this road takes me, and I guess the journey will start tomorrow," he said.

Phelps was last seen in the 2012 London Olympics and said that he gained 30 pounds after the event. Coming into Mesa, he has made progress in losing the extra weight to be at his best. He said that the period between the 2008 Beijing Olympics and the 2012 London Olympics was the most challenging for him as a sportsperson.

"Getting back into shape was the number one thing," the American said.

"Going into 2012, it was hard. There were a lot of ups and downs. It was very challenging at times to get motivated."

Having participated in four Olympics - winning as many as 22 medals (18 gold) - does his return to plunge hint at the goal of a fifth Olympics in Rio 2016? Phelps replied he is only excited about the present.

"I just missed being back in the water," said Phelps. "It's been fun. We'll see what happens here, who knows.

"I always have goals and have things I want to achieve, and I have things that I want to achieve now.

"In terms of tarnishing my career, I said it before, I'm doing this for me," Phelps said when asked if he fears his return might tarnish the remarkable achievements so far. "If I don't become as successful as you all think I would be or should be, and you think it tarnishes my career, then that's your own opinion."

(Ed: VP)