The daughters of Danaos, king of Argos, they were punished for murdering their husbands. After their death, they were sent to Tartaros (not heaven, the other place) and forced to carry water and pour it into a broken cistern for all eternity. A futile labor that lasts forever.

Danaos, a grandson of Poseidon and Libya, had a dispute with his brother, Aegyptos. Danaos and his fifty daughters sailed to Argos, and was kindly received by the king. At that time there was a deadly drought, and Danaos sent his daughters to find a spring and bring back some water. One of them, Amymone, threw a spear at a stag, but hit a sleeping satyr instead.

The satyr chased Amymone, who called on Poseidon for help. Poseidon drove off the satyr, and impressed by her beauty, took Amymone, who bore a son to Poseidon.

Aegyptos proposed to forget their differences with his brother, Danaos who, gave the sons of his brothers his own daughters as wives.
However, Danaos gave each of the daughters a knife to kill their husbands on their wedding night. All but Hypermnestra agreed, and as a result she was spared the fate her sisters suffered after their deaths.

Danaos threw Hypermnestra in a dungeon, but later she was acquitted, and succeeded Argos to the throne, ruling for many years.

The other daughters, afer their death, were forced to carry water and pour it into a broken cistern for all eternity.