Luckless Jason Day has suffered a watery grave as Russell Henley produced a lightning finish to win the Arnold Palmer Invitational in the maverick style of the late tournament host. Henley trailed Collin Morikawa by three shots with five holes to play before reeling his fellow American in with a pair of two-shot swings at the famed and baked-out Bay Hill Golf Club. Henley chipped in for eagle at the 16th hole in the decisive play of the day en route to a final-round two-under-par 70 and his first victory since the 2022 World Wide Technology Championship. He prevailed by one shot over third-round leader Morikawa, who could only manage a even-par 72. Bidding to join world No.1 and defending champion Scottie Scheffler as a two-time winner of the PGA Tour's $US20 million ($A32 million) Signature event, Day pulled to within two shots of the lead midway through the back nine. But Australia's former world No.1 was left cursing his rotten luck after dunking his mud-laden ball into the drink on the par-5 16th. Day racked up a double bogey to wind up tied for eighth at five under, six strokes behind Henley after signing for a two-over 74 as Henley held his nerve to claim a fifth PGA Tour win. "Hats off to Collin, he played great, super-steady, but sometimes golf is just mean like that," the humble Henley said. "I was so nervous, so unbelievably nervous. Look, I can't breathe right now. It's so hard and so difficult around this place. "I got a good break there (on 16), I holed another one there yesterday on the first hole from the bunker and had a couple of hole-outs off the green this week. "I just tried to stay really tough. I've watched Tiger (Woods) make a lot of putts on this green. I've watched Rory (McIlroy), Fran (Francesco Molinari) and Bryson (DeChambeau) make winning putts here, and it's cool to know I did it too." Henley, a 35-year-old Georgia native who will rise to world No.7, will be hoping his victory proves an omen ahead of next months' Masters. Scheffler donned the green jacket both times after winning at Bay Hill in 2022 and 2024. Morikawa, whose last victory was in October 2023, will be wondering what might have been. The two-time major champion led by three mid-round but took bogey on the 14th and couldn't buy a birdie down the stretch. Canadian Corey Conners (71) finished third at nine under to secure a ticket to the 153rd British Open in July at Royal Portrush.