Contestants frequently hook up on the show. Some do it for fun, while others are emotionally connected to each other.
Women sometimes get naked and swim in the pool. This is the case most notably in Invasion of the Champions where 3 women sit next to each other in a pool naked. There is also a pool filled with naked women on Vendettas.
On Final Reckoning, three couples are having sex in the same room. One women asks the other man to take their dick out and later performs oral sex on him. That same man later jumps out of bed and leaves the room. At another point during that season, a women asks anyone if they have ever given oral sex before, and one women admits to it.
Hookups often play a big part in the drama in the house, especially if someone cheats on someone else.
A power couple has sex on WOTW1. We don't see the act since there are blankets covering their bunk bed, but we do hear moaning. They are overheard by a group of people, one of them being the ex of one of the people having sex.
On Final Reckoning, 3 couples have sex in the same room. One women asks the other man to pull his dick out and the women performs oral sex on him. A man later jumps out of bed naked and walks out of the room.
In many sexual situations, players are seen making out with other players under the covers of a bed and it is heavily implied that they have sex.