Watson was almost dismissed in Tremlett's next over when Strauss failed to hold on to a catchwell above his head, but once again England's disappointment was short-lived.
He struck eight fours and a six in a commanding innings that ended eight short of a deserved century in the 47th over when he lofted Clint McKay to wide long-on where Doug Bollinger held a well-judged catch.
Paul Collingwood kept the scoreboard ticking by swiping Jacques Kallis for six over mid-wicket before Kieswetter, after thumping Duminy for six in similar fashion, fell to the same bowler when he holed out to Steyn, who took a well-judged catch fractionally inside the rope at long-on.