By Mark Lamport-Stokes
With Michael working as his caddie, the 60-year-old Watson charged to the top of the early leaderboard with a vintage performance at a breezy Augusta National.
The tousle-haired American, who came agonizingly close to the most remarkable major victory of all time before losing the 2009 British Open at Turnberry in a playoff, signed off with a six-foot birdie putt at the last.
"A big part of my success today was having my son on the bag," a beaming Watson told reporters after hugging Michael on the 18th green.
"He said: 'Dad, show me ... you can still play this golf course'. You know what, I wanted to show him I can still play the golf course.
"I did what I had to do today and took advantage of some of the holes you could take advantage of," said Watson, a double champion at Augusta who has missed the cut here for the last seven years.
"I had a little bit of a different frame of mind going into this week. It seemed to help a little bit. The last four or five years I've gone into the tournament feeling like the course was too big for me.
"Today, as it was last year, the course was set up where you could get to some of the pins."
Watson, whose remarkable bid for a British Open victory at the age of 59 ended when he lost to fellow American Stewart Cink in a playoff last July, had clear targets in mind when he teed off.
"My goals were to play better than I've played in the last five or six years and I achieved that for the first round," the eight-times major champion said.
"I have to play better than 90 percent to be successful on this golf course.
"My driving has been very good, that's been much better than 90 percent. My iron game is just a little questionable.
"My putting is, I would have to say, above 90 percent so I'm above that 90 percent threshold. So I give myself a decent chance from that perspective."
Champion here in 1977 and 1981, Watson felt experience was a significant factor at the Masters.
"There's a lot of experience you have to use to play this golf course," he said after covering the back nine in three under. "You know that you have to put the ball in certain positions or you're going to make bogey."
Asked if he was capable of emulating his Turnberry performance by staying in contention for all four days, he replied: "I don't know. Ask me after Sunday's round."
(Editing by Tony Jimenez)