The chart-topping singer, who plays Petty Officer Cora Raikes in the sci-fi adventure, was put through her paces by a no-nonsense soldier.
She said: "I had to do a lot of physical training. I had to do push-ups, tons of push-ups. I hate them!"
Rihanna, 24, went on: "I had to work out with these sandbags that were the same weight as the weapon and I had to get used to pulling them around. The trainer would make me do it like 40 times back to back, until one of my arms literally was so dieselled (defined) and the other one was so regular."
The star, who makes her acting debut in the movie, continued: "He yelled at me so many times. It was crazy. But it really put me in that place so it was necessary.
"I thought, 'There's no way he's coming into my room, talking to me like that'. After a while, I got so freaked out, he messed up my head. Every time he came over, I would hide all my high heels, any shopping bags, remove my pink iPod from the dock - and no, I didn't have nails! The first time he came over, he saw them and said, 'You have to be kidding me'. I got rid of those so fast."
As the feisty Raikes, the singer got to grapple with aliens and handle big guns.
"That was the cool part - I got to shoot a lot of weapons and kick a lot of alien butt!" she recalled.
:: Battleship opens in cinemas on Wednesday, April 11.
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