JOIN USSpaniard Jimenez shoots into lead
While three-times champion and heavy favourite Tiger Woods struggled to a one-over-par 71, fellow American Watson fired a flawless 65 on a surprisingly calm day at the Ailsa Course.
"She was defenceless today," Watson, 59, told reporters of the par-70 coastal layout. "The golf course played with no wind and it was an easy test, if you have an easy test in an Open championship.
"I feel inspired playing here, being in the presence of Turnberry again, just a culmination of a lot of things that have gone on already. I feel I'm playing well enough to win the golf tournament."
Thirty-two years ago, Watson outduelled Jack Nicklaus to win the first Open staged at Turnberry.
Asked to explain why so many old hands had flourished on Thursday, five-times champion Watson replied: "We have an advantage.
"The pros don't play links golf except in the Open championships or the Senior Open championships.
“We've played under these conditions and we kind of get a feel for it and that feel is worth its weight in gold when you're playing."
Australian John Senden, a late addition to the field after the withdrawal of Indian Jeev Milkha Singh on Tuesday due to a rib injury, birdied four of the last six holes for a 66.
Also at four under were in-form Steve Stricker, who has won twice on the PGA Tour in his last four starts, fellow American Stewart Cink, Australian Mathew Goggin and Colombia's Camilo Villegas.
Much of the early running, though, was dominated by senior players with former winners Mark Calcavecchia, 49, Mark O'Meara, 52, and Vijay Singh, 46, carding matching 67s.
Calcavecchia, who teed off in the first group of the day on a sun-splashed morning, quickly made the most of the conditions.
"The weather was perfect," the 1989 winner told reporters. "There was no wind and the early start doesn't bother me. I played well.
"I hate to say Turnberry was easy, because it's a really hard course, but if you're going to shoot a good score out there, today was the day to do it."
Woods, however, had a day to forget as he pushed several shots to the right and three times hurled a club to the ground in frustration.
"I certainly made a few mistakes out there today," the 33-year-old said after carding four bogeys and three birdies.
Double British Open champion Greg Norman also struggled, a birdie-birdie finish taking little sting out of an opening 77.