In Hold Your Breath!, the game is played in two rounds. In the first round each player may dive deeper, providing they have the "Swim" and "Air" cards to do so. Players press their luck each turn since it is the pirate who dives the deepest in round one AND resurfaces in round two who is the winner. Players can play "Panic", "Shark" and other nasty cards on the other players, slowing their progress. In the second round each player struggles to reach the surface before they run out of air and therefore decide to take a rest (aka LOSE). Most of the pirates may not make it back to the surface, but the one who makes it back alive AND dove the deepest is the winner.
This expansion allows for up to two additional players to take a dive and press their luck.