'Survivor: Blood vs. Water' Premiere: First Look at Immunity Challenge (Exclusive Photos)

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Timothy Kuratek/CBS

Host Jeff Probst (in the blue shirt) oversees -- and, of course, narrates -- all the action from the sidelines.

Viewers get their first look at Survivor: Blood vs. Water on Wednesday night.

The 27th season of the CBS reality competition, which premieres with a special 90-minute episode at 8 p.m., features 20 new castaways competing for the $1 million prize. The twist this season? Ten of them are previous competitors -- and the other 10 are their loved ones. (Hence, the "blood vs. water" subtitle.)

PHOTOS: 'Survivor: Blood vs. Water': Meet the Returning Players (Again) and the Loved Ones They'll Compete With

The Hollywood Reporter has a first look at the immunity challenge on Wednesday's premiere episode, titled "Blood Is Thicker Than Anything." (Click here for more photos.) In a video posted on CBS' website last week, challenge producer John Kirhoffer revealed what the challenge -- dubbed "Blue Lagoon Bustle" -- entails.

As he explained, the castaways race into the water, where they are forced to overcome a series of obstacles, including climbing up and over a net, going over a barrel roll, climbing up on crates and swimming out to a boat, where they must untie a series of knots and race the boat back. They then must compete a puzzle; the first tribe to do so wins immunity -- and, of course, a guaranteed three more days in the game. (Watch the video of the challenge rehearsal crew taking part below.)

PHOTOS: 'Survivor: Blood vs. Water' Premiere: Exclusive First Look at Immunity Challenge

As previously revealed, this season also will feature the return of Redemption Island, where castaways who have been eliminated from the game can seek redemption and return for a chance to win the $1 million prize. The twist this season, however, is loved ones will be forced to choose whether to "save" their partner on Redemption Island and switch places with them, thus allowing their loved one to immediately re-enter the game, or leave them in exile to survive on their own.