Rihanna vs. Jennifer Aniston—Who's Got the Hottest Water Ad?

Both beauties chosen to model in new water ads, but who looks sexier doing it?

Both Rihanna and Jennifer Aniston make the ordinary human act of hydration look really, really, really good.

Aniston is showing off her abs and rolling in the sheets with her bottle in new black-and-white ads for Smartwater, while Rihanna is modeling for Madonna's Vita Coco, lounging on a beach in a white sundress while doing some sultry sipping from a straw.

So, whose ad is hotter? Let's go to the evidence...

Rihanna's Vita Coco ads will debut this summer. The beach-loving Barbados native is no stranger to the tropics, so she's a great choice for hawking coconut water.

The singer, still rocking her red hair, is also an investor in the company along with Matthew McConaughey and Demi Moore. 

But enough background, does this beachy shot make her look hotter than Jen?

Speaking of Aniston, she's been shilling for Smartwater with humor—and even had a video ad for the company go viral. In the new campaign she's rocking two different looks, one for day and one for night, where she is seen exiting a black car in a little black dress, holding a bottle of the stuff.

The pics were shot by famed photog Steven Klein back in February and will hit mags in June.

Either way, these ladies are making us thirsty.