Joe: he won by cannonball-jumping into a hot tub with a couple inside.
Murr: he won by applying sunscreen all over a random man. The man was chosen by the other guys. Murr won by talking about something else and distracting him.
Sal: was originally supposed to tell some young kids in the pool about "the birds and the bees". However, after much hesitation, it looked like he wouldn't do it. Q decided on an alternative for Sal—drink pool water. He must do either of those or he will get a Loss. He ultimately decides to drink the pool water and gags afterward. However, he was let off with a win.
Q: after he forced Sal to drink the pool water, Sal got his revenge by making Q drink pool water for his challenge. He was feeling the harsh revenge, but was allowed to win if he explained the birds and the bees to the earlier kids. He explained it to them as simple as possible and received a win. Nobody lost.