Inconsistency has blighted Henrik Stenson's hopes of winning a second Commercialbank Qatar Masters title.
The Swede was some way off the pace when he started his second round in his golf clothing, but a superb 31 for the first nine holes saw him charge back into the chasing pack.
However, he came home in 42 and allowed his frustration to get the better of him as he flung his wedge into the lake after a triple bogey.
Clubhouse leaders Thomas Aiken and Paul Lawrie are four under par, with the latter carding an excellent 66.
Stenson, who won the title in 2006, holed birdies at 14, 16 and 17 before scoring a superb eagle on 18 to head to the last nine four shots behind the leaders.
But he lost his cool and embarked on a terrible run of form as his chances of reclaiming the title he won in 2006 disappeared like his golf club in the water hazard.
Overnight leader Retief Goosen held his nerve over the first five holes to retain a share of the lead and will be looking to edge ahead of fellow South African Aiken.
Meanwhile, Englishman David Howell recovered from his first round 75 to finish with a 69 that will see him comfortably make the cut.