Four sports that all happen in water; water polo, swimming, synchronised swimming and diving.
Everyone knows how the swimming works, although swimmers will have to be wary as if they make a single false start in their event they will be disqualified.
Normally Olympic swimming happens solely in the pool, but at the Beijing Games in 2008, open water swimming was introduced.
In that event swimmers are outside and race over 10km. It can get a bit rough under the water too, with pushing, pulling and scratching all common!
Diving takes place from a series of high boards, with judges scoring on the difficulty of the dive and the skill of completing it.
Synchronised swimming sees pairs or groups of swimmers 'dance' to music. They must complete the complicated moves at the same time to score well.
In water polo, swimmers try to throw the ball into a goal, a bit like football. Amazingly, players aren't allowed to touch the sides or the bottom of the pool during the game, so they have to keep treading water.