But the combination of overloaded boats and choppy waters meant the blonde star and her fellow actors got soaked by crashing waves of river water before they could dock on the HMS Belfast, which was stationed near Tower Bridge.
Twenty-seven-year-old Sienna, took it all in her stride though. "Thank God I've got a skin-coloured something underneath, otherwise I would be horribly regretting the white shirt," said the actress, who never lost her smile. "I'm soaking wet, but I did actually enjoy it."
In the film, which opens in the UK on August 7, an elite military team journeys the planet to track down an arms dealer. Sienna plays a villain, The Baroness.
Whether her character meets a sticky end remains to be seen, but one thing's for sure – if her character does die, her dad won't be pleased.
She revealed this week that while her parents are proud of her acting work, her father Edward particularly hates seeing his daughter in harrowing or raunchy scenes – so she has to shield him from those clips.
"My parents are very supportive of my work, but they hate seeing me die, overdose or have sex on screen. I have to cover my dad's eyes for those parts," she admitted.