The agency will create the sports drink brand's first advertising for two years. Work, including television and outdoor executions, is expected to break in the summer.
Aquarius first launched in Japan in 1983, where the grapefruit-flavoured water was positioned as a rehydrating sports drink. It is now distributed in 15 countries across Asia and Europe including the UK, Spain, Portugal, France and Indonesia.
Mustoes' appointment to the Aquarius business follows Coca-Cola's decision to rejig its marketing budget with a focus on health, wellness and performance drinks.
In November 2005, the soft-drinks giant created a dedicated Health and Wellness arm. The division is led by the marketing manager, Sarah Marsh, who oversaw the UK launch of the Minute Maid orange juice brand in 2004.
The division houses the company's healthier drink options, which include Minute Maid and Oasis. The reorganisation is also intended to give greater emphasis to new-product development.
Although Coca-Cola has doubled the number of products and brands it distributes in the UK over the past ten years, some of its brands have suffered from ongoing consumer concerns about obesity and the effect consuming high-sugar fizzy drinks can have on health.
Mustoes and Coca-Cola both declined to comment on the appointment.