Watch Series Survival of the Fittest Online at Couchtuner. Survival of the Fittest sees a group of young, hot singles living together under the searing sun as they take part in the ultimate battle of the sexes, in order to win a big cash prize. A team of girls and a team of boys will battle it out in a series of stunning physical and mental challenges to determine which sex has the upper hand, while romantic dates will test their loyalties to the limit. Will the girls put sisters before misters and will the boys choose mates over dates? Or will the temptation be too much and they end up in bed with the enemy?