Survivor: Blood vs. Water's cast and twists -- which will include the return of Redemption Island -- have been officially revealed.

CBS has announced the identities of the 20 castaways who will be competing on Survivor: Blood vs. Water, the 27th Survivor edition which will premiere Wednesday, September 18 at 8PM ET/PT with a special 90-minute episode.

As the network previously announced, Survivor: Blood vs. Water -- which was filmed this past May and June in the Philippines -- will feature 10 returning Survivor castaways initially competing against a second tribe comprised of 10 family members and loved ones.

In addition, Redemption Island will allow castaways who get voted out of their tribe to have the chance to compete in "duel" challenges for a chance to return to the game and resume competing for the $1 million grand prize.

However, unlike prior Redemption Island seasons, Survivor: Blood vs. Water will enable each castaway's loved one to determine whether they want to "save" and switch places with their partner when they are voted out of their tribe -- allowing the voted-off partner to immediately re-enter the game on the other tribe -- or allow them on go to Redemption Island to fend for themselves.

Survivor host Jeff Probst revealed additional details about the season's gameplay during an on-set visit with Entertainment Weekly.

For the first time in the show's history, the game will reportedly take place over 39-and-a-half days. Dubbed the "Day Zero" twist, the game will begin the night prior to Day 1 with the 10 pairs getting distributed to 10 different locations, where they will spend the night. Probst will then gather all the pairs together the following morning, splitting up the returning players and their loved ones into two different tribes.

"The whole idea was to try and get them thinking and maybe believing that they would play as a pair," Probst told EW. "Suddenly your partner becomes your adversary, your competition. And that was the whole premise of Blood vs. Water. How is that going to play out in a game where only one person can win?"

The returning players will reportedly make up the yellow Galang tribe, while the newbie players will join forces on the comprising Tadhana tribe, who will wear red.

Right after getting formed, each tribe will also be surprised with the news that they have to vote off one of its own members immediately, and those two castaways will -- unbeknownst to the players who gave them the boot -- reportedly head straight to Redemption Island. The Redemption Island twist willthen  be revealed to the players later in the game.

Despite still being termed "duels," each duel challenge will reportedly feature three castaways -- with the last-place finisher getting eliminated from the game for good and the first-place finisher receiving a bonus clue to where a hidden Immunity Idol is hidden. The winner will be afforded the opportunity to give that clue to any one person on either tribe.

"There's all these things you can do," said Probst. "Because for a moment, even though you're on the outest, furthest part of the game, you have a little bit of power."
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Loved ones will also have the option to switch places with their partners on Redemption Island right before a duel, according to EW. If the challenge seems strength-related, for example, a husband may want to swap positions with his wife at that time and attempt the task while she hangs out in his tribe.

Pairs can strategically elect to switch places at every duel thereafter until they lose a duel entirely.

"That puts blood and water to the test," Probst explained. "And we're gonna do it at every duel. So the first time early in the game, somebody may say 'It's just too early.' But as those duels increase and they get closer to what they think might be a merge, their strategy is going to start to change."

The 10 returning Survivor castaways are Tyson Apostol, Aras Baskauskas, Rupert Boneham, Candice Cody (formerly known as Candice Woodcock), Monica Culpepper, Colton Cumbie, Kat Edorsson, Laura Morett, Gervase Peterson, and Tina Wesson.

Culpepper, Cumbie and Edorsson all originally competed on Survivor: One World, which aired in early 2012. Culpepper, a 42-year-old former NFL wife and homemaker from Tampa, FL, was voted out of her season in fifth place and will return to compete with her husband Brad Culpepper, a 44-year-old attorney and retired NFL player from Tampa, FL.

Cumbie was the sixth castaway eliminated from Survivor: One World via a medical evacuation. For Survivor: Blood vs. Water, Cumbie -- a 22-year-old student teacher from Collinsville, AL -- will compete with fiance Caleb Bankston, a 26-year-old post office manager and farmer from Collinsville, AL.

Edorsson, a 23-year-old full-time student and saleswoman from Orlando, FL, finished in seventh place during her stint on Survivor: One World. She will pair up with her boyfriend -- former Big Brother winner Hayden Moss, a 26-year-old in real estate from Springtown, TX.

Apostol, a 34-year-old former pro cyclist and shop manager from Provo, UT, was the ninth castaway eliminated on Survivor: Tocantins, which aired in early 2009, and the sixth castaway voted off Survivor: Heroes vs. Villains, which aired the following year. Apostol will compete with girlfriend Rachel Foulger, a 33-year-old cocktail waitress and graphic designer from Provo, UT.

Baskauskas, a 31-year-old musician from Santa Monica, CA, was crowned champion of Survivor: Panama -- Exile Island, which aired in early 2006. He will compete with his brother Vytas Baskauskas, a 33-year-old yoga instructor and math professor from Santa Monica, CA.

Boneham, a 49-year-old mentor for troubled teens from Indianapolis, IN, was the fifteenth person voted out of Survivor: Heroes vs. Villains and the tenth castaway voted out of Survivor: Pearl Islands, which aired in Fall 2003. He also finished in fourth place during Survivor: All-Stars, which aired in early 2004.

Boneham will compete alongside wife Laura Boneham, a 44-year-old merchandiser from Indianapolis, IN.

Morett, a 43-year-old co-owner of Morett Construction from Salem, OR, was the eleventh castaway eliminated from Survivor: Samoa, which aired in Fall 2009. She will compete with her daughter Ciera Eastin, a 24-year-old cosmetology student from Salem, OR.

Peterson, a 43-year-old cigar lounge owner from Philadelphia, PA, finished seventh place on Survivor: Borneo, which aired in Fall 2000. He will compete on Survivor: Blood vs. Water with his niece Marissa Peterson, a 21-year-old student from Chapel Hill, NC.

Cody finished in eighth place on both Survivor: Heroes vs. Villains and Survivor: Cook Islands, which aired in early 2006. The 30-year-old physician and anesthesiology resident from Washington, D.C., will compete with husband John Cody, a 30-year-old physician and army orthopedic surgery resident from Washington, D.C.  

Wesson, a 52-year-old motivational speaker from Robbinsville, NC, won Survivor: Australia -- which aired in early 2001 -- and was the first person voted out of Survivor: All-Stars. Wesson will compete with her daughter Katie Collins, a 25-year-old who works in hedge fund support from New York, NY.