Tron: Legacy actress Beau Garrett and Shameless' Justin Chatwin are joining a celebrity group scaling Mount Kilimanjaro to raise awareness of the global clean water crisis.

The Hollywood stars are making the trek with Foster The People frontman Mark Foster and singer Kenna, who organised the Summit On The Summit: Kilimanjaro climb up Africa's tallest peak.

On Thursday (03Jan12), the hikers arrived in Tanzania ahead of their gruelling seven-day, 50-mile (80-kilometre) journey up Kilimanjaro.

The stars will use social media to draw attention to the problem of water-borne illness and disease, and will be supported by actresses/activists Olivia Wilde and Dianna Agron as they blog about the mission online.

Glee star Agron has tweeted, "Good luck Kenna & everyone on Summit On The Summit 2! So sad that I couldn't make this climb!! I am sending my love & support from over here!!"

Jessica Biel, Emile Hirsch, Isabel Lucas and rapper Lupe Fiasco joined Kenna on his first celebrity Summit adventure in 2010.